Parathyroid hormone-related protein and its receptor in human glial tumors

OBJECTIVE

Parathyroid hormone-related protein (PTHrP) and its mRNA have been found to be expressed in a variety of human tumors including breast, prostate, colon, lung, renal and ovarian cancers. The purpose of this study is to evaluate the expression of PTH/PTHrP receptor and ligand in human glial tumors.

METHODS

We examined the coexpression of PTH/PTHrP receptor and ligand in 73 glial tumors of different histological grades and 4 nonneoplastic human brain specimens and three glioblastoma cell lines, by using Western Blot analysis and immunohistochemical analysis.

RESULTS

PTHrP and PTH/PTHrP receptors were shown in the neurons, reactive astrocytes and the endothelial cells of normal brain tissue as well as tumor cells, reactive astrocytes and vasculature of nonneoplastic tissue. They were expressed at higher levels in pure astrocytic tumors as compared to tumors with oligodendroglial components.

CONCLUSION

PTH/PTHrP receptor and PTHrP ligand are co-expressed in human glial tumors. There increased expression suggests an autocrine and/or paracrine loop may exist.

Severe defect in proglucagon processing in islet A-cells of prohormone convertase 2 null mice

Mice homozygous for a deletion in the gene encoding prohormone convertase 2 (PC2) are generally healthy but have mild hypoglycemia and flat glucose-tolerance curves. Their islets show marked alpha (A)-cell hyperplasia, suggesting a possible defect in glucagon processing (Furuta, M., Yano, H., Zhou, A., Rouille, Y., Holst, J., Carroll, R., Ravazzola, M., Orci, L., Furuta, H., and Steiner, D. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 6646-6651). In this report we have examined the biosynthesis and processing of proglucagon in isolated islets from these mice via pulse-chase labeling and find that proglucagon undergoes essentially no processing in chase periods up to 8 h in duration. Only a small percent of cleavage at the sensitive interdomain site (residues 71 and 72) appears to occur. These observations thus conclusively demonstrate the essentiality of PC2 for the production of glucagon in the islet A-cells. Ultrastructural and immunocytochemical studies indicate the presence of large amounts of proglucagon in atypical appearing secretory granules in the hyperplastic and hypertrophic A-cells, along with morphological evidence of high rates of proglucagon secretion in PC2 null islets. These findings provide strong evidence that active glucagon is required to maintain normal blood glucose levels, counterbalancing the action of insulin at all times.

Effectiveness of lateral slide exercise in an anterior cruciate ligament reconstruction rehabilitation home exercise program

STUDY DESIGN

Two-group repeated measures design using a sample of convenience of subjects with anterior cruciate ligament (ACL) reconstructive surgery.

OBJECTIVES

To determine the effect of incorporating one specific weight-bearing exercise (lateral slide exercise using a slide board) into an ACL reconstruction home exercise program.

BACKGROUND

Reduced clinic visits have increased the importance of home exercise programs in knee ligament reconstruction rehabilitation. Few studies have been conducted to test the efficacy of specific exercises as part of a home-based treatment program on subjects who have undergone ACL reconstruction.

METHODS AND MEASURES

Fourteen subjects who underwent patella tendon autograft reconstruction on one of their ACLs were studied. Testing consisted of the following 4 measurements: peak isometric knee extension torque, peak isometric knee flexion torque, maximum lateral step height, and lateral step-up repetitions to fatigue. Subjects were pretested at 8 weeks after surgery and were randomly placed into either a control or experimental group. The postsurgical rehabilitation was similar for both groups, except the experimental group incorporated lateral slide exercise into their home exercise program. All subjects were re-evaluated 14 weeks after surgery.

RESULTS

A 2-way repeated measure ANOVA (group by test session), and posthoc testing revealed significant improvements in the slide group for quadricep strength (101.9 +/- 31.3 N m to 140.5 +/- 31.3 N m of torque), while the control group showed no significant increase (125.1 +/- 61.7 N m to 125.8 +/- 45.1 N m of torque). Lateral step height also improved in the slide group (from 22.9 +/- 5.3 cm to 28.7 +/- 5.6 cm), while the control group showed no increase (20.0 +/- 4.5 cm to 20.7 +/- 3.4 cm). Both groups increased in lateral step-up repetitions to fatigue.

CONCLUSION

Including lateral slide exercise in a home exercise program after ACL reconstruction appears to improve knee extension strength.

Regulation of secretion of PTHrP by Ca(2+)-sensing receptor in human astrocytes, astrocytomas, and meningiomas

Parathyroid hormone-related protein (PTHrP) is the major mediator of the humoral hypercalcemia of malignancy and of malignant osteolysis associated with skeletal metastases of common epithelial cancers. PTHrP secretion is regulated by the extracellular calcium concentration ([Ca(2+)](o)) in several types of normal and malignant cells. Because the [Ca(2+)](o)-sensing receptor (CaR) is a key mediator of [Ca(2+)](o)-regulated hormone secretion [e.g., of parathyroid hormone (PTH) by parathyroid chief cells], we investigated the expression of the CaR and PTHrP in normal and neoplastic glial cells and studied the effects of [Ca(2+)](o) on PTHrP secretion. Our results show that primary embryonic human astrocytes (HPA) express CaR mRNA and protein as detected by RT-PCR and Western analysis, respectively. Furthermore, astrocytomas and meningiomas also express the CaR at similar levels as assessed by RT-PCR and Northern and Western blot analyses. HPA and astrocytomas express transcripts encoding all three known isoforms of PTHrP [PTHrP(139), PTHrP(141), and PTHrP(173), comprising 139, 141, and 173 predicted amino acid residues, respectively] as assessed by RT-PCR, whereas meningiomas express only the first two of these. Finally, elevated levels of [Ca(2+)](o) and other polycationic CaR agonists dose dependently stimulate PTHrP secretion from HPA, astrocytomas, and meningiomas, although both basal and high [Ca(2+)](o)-stimulated rates of PTHrP secretion are approximately 2. 5-fold higher in HPA than in the glial tumors studied here. Therefore, our results show that HPA, astrocytomas, and meningiomas express both the CaR and PTHrP and that CaR agonists stimulate PTHrP secretion.

Kin-cohort designs for gene characterization

BACKGROUND

In the kin-cohort design, a volunteer with or without disease (the proband) agrees to be genotyped, and one obtains information on the history of a disease in first-degree relatives of the proband. From these data, one can estimate the penetrance of an autosomal dominant gene, and this technique has been used to estimate the probability that Ashkenazi Jewish women with specific mutations of BRCA1 or BRCA2 will develop breast cancer.

METHODS

We review the advantages and disadvantages of the kin-cohort design and focus on dichotomous outcomes, although a few results on time-to-disease onset are presented. We also examine the effects of violations of assumptions on estimates of penetrance. We consider selection bias from preferential sampling of probands with heavily affected families, misclassification of the disease status of relatives, violation of Hardy-Weinberg equilibrium, violation of the assumption that family members' phenotypes are conditionally independent given their genotypes, and samples that are too small to ensure validity of asymptotic methods.

RESULTS AND CONCLUSIONS

The kin-cohort design has several practical advantages, including comparatively rapid execution, modest reductions in required sample sizes compared with cohort or case-control designs, and the ability to study the effects of an autosomal dominant mutation on several disease outcomes. The design is, however, subject to several biases, including the following: selection bias that arises if a proband's tendency to participate depends on the disease status of relatives, information bias from inability of the proband to recall the disease histories of relatives accurately, and biases that arise in the analysis if the conditional independence assumption is invalid or if samples are too small to justify standard asymptotic approaches.

Designing studies to estimate the penetrance of an identified autosomal dominant mutation: cohort, case-control, and genotyped-proband designs

One can obtain population-based estimates of the penetrance of a measurable mutation from cohort studies, from population-based case-control studies, and from genotyped-proband designs (GPD). In a GPD, we assume that representative individuals (probands) agree to be genotyped, and one then obtains information on the phenotypes of first-degree relatives. We also consider an extension of the GPD in which a relative is genotyped (GPDR design). In this paper, we give methods and tables for determining sample sizes needed to achieve desired precision for penetrance estimates from such studies. We emphasize dichotomous phenotypes, but methods for survival data are also given. In an example based on the BRCA1 gene and parameters given by Claus et al. [(1991) Am J Hum Genet 48:232-242], we find that similar large numbers of families need to be studied using the cohort, case-control, and GPD designs if the allele frequency is known, though the GPDR design requires fewer families, and, if one can study mainly probands with disease, the GPD design also requires fewer families. If the allele frequency is not known, somewhat larger sample sizes are required. Surprisingly, studies with mixtures of families of affected and non-affected probands can sometimes be more efficient than studies based exclusively on affected probands when the allele frequency is unknown. We discuss the feasibility and validity of these designs and point out that GPD and GPDR designs are more susceptible to a bias that results when the tendency for an individual to volunteer to be a proband or to be a subject in a cohort or case-control study depends on the phenotypes of his or her relatives.

Delayed cardioprotection in a human cardiomyocyte-derived cell line: the role of adenosine, p38MAP kinase and mitochondrial KATP

Evidence of delayed preconditioning (PC) in man is limited. Adenosine is proposed as a trigger via action on the A1 receptor in many species and the mitochondrial KATP channel is a likely end effector. We examined the ability of a brief, simulated ischemic episode on day one to provide delayed cardioprotection against lethal, simulated ischemia on day two in a human cardiac cell line with reference to the role of adenosine, the p38MAP kinase signalling pathway and mitochondrial KATP channel.

RESULTS

PC and adenosine administered on day 1 protected against cell death on day 2 as measured by LDH release and propidium iodide (PI) exclusion: (%LDH release: PC: 12.1 +/- 1.1%, ADO: 11.9 +/- 2.0% vs control: 36.4 +/- 1.1%; %PI positive: PC: 14.6 +/- 1.4%, ADO: 17.9 +/- 2.0% vs control: 34.4 +/- 2.0% respectively). This protection is abolished by treatment with SB203580 prior to the protective stimulus on day 1: [PC + SB (%LDH release 28.6 +/- 2.8%; %PI positive 34.7 +/- 2.2%) and ADO + SB (%LDH release 25.3 +/- 2.9%; %PI positive 33.7 +/- 7.3)]. Similarly 5-hydroxydecanoate abolished protection, when given immediately prior to lethal simulated ischemia on day 2: [PC + 5-HD; (%LDH release 31.9 +/- 4.8%; %PI positive 29.5 +/- 2.0%) and ADO + 5-HD (%LDH release 36.9 +/- 4.0%; %PI positive 34.8 +/- 2%)].

CONCLUSION

In this model delayed PC can be mimicked by adenosine and involves the p38MAP kinase pathway and the mitochondrial KATP channel.

SB 203580, a mitogen-activated protein kinase inhibitor, abolishes resistance to myocardial infarction induced by heat stress

Heat stress (HS) is known to confer protection against ischemia-reperfusion injury, including mechanical dysfunction and myocardial necrosis. However, the mechanisms involved in this cardioprotection are yet to be elucidated. Mitogen-activated protein (MAP) kinase cascades have been demonstrated to be involved in cellular response to different stresses. In particular, p38 MAP kinase is known to be activated by HS. Therefore, we investigated the implication of this kinase in HS-induced resistance to myocardial infarction, in the isolated rat heart model, using SB 203580 (SB) to selectively inhibit p38 MAP kinase. Rats were treated with SB (2.83 mg/kg, i.p.) or vehicle (1% DMSO in saline, i.p.) before they were either heat stressed (42 degrees C for 15 minutes) or sham anesthetized. Their hearts were isolated 24 hours later, retrogradely perfused, and subjected to a 35-minute occlusion of the left coronary artery followed by 120 minutes of reperfusion. The infarct-to-risk ratio was significantly reduced in HS (16.9 +/- 2.0%) compared with sham (41.6 +/- 2.5%) hearts. This reduction in infarct size was abolished in the SB 203580-treated group (37.8 +/- 1.9% in HS + SB vs. 42.0 +/- 1.9% in sham + SB). Risk zones were similar between experimental groups. Western blot analysis of the myocardial HSP72 showed an HS-induced increase of this protein, which was not modified by the p38 MAP kinase inhibitor, SB 203580. We conclude that activation of p38 MAP kinase appears to play a role in the functional cardioprotection associated with the heat stress response, which seems to be unrelated to the HSP72 level. Further investigations are required to elucidate the precise role of the p38 MAP kinase and heat stress proteins in this adaptative response.

Distinct roles for ionotropic and metabotropic glutamate receptors in the maturation of excitatory synapses

We used the single-cell culture preparation to study the role of activity in the development of glutamatergic synapses in vitro. Rat hippocampal cells grown in isolation on glial islands formed functional autaptic connections and continued to elaborate new synapses throughout the 2 week investigation, resulting in increases in both the evoked AMPA receptor (AMPAR) and NMDA receptor (NMDAR) components of the EPSC. Synaptogenesis was not prevented by chronic blockade of sodium channels or all of the known glutamate receptors. Analysis of miniature EPSCs revealed that AMPAR quantal size doubled over time in vitro whereas NMDAR quantal size remained constant. However, the proportion of synaptic responses mediated only by NMDARs increased over time in vitro. The increase in AMPAR quantal size was prevented by TTX and ionotropic glutamate receptor antagonists, whereas the increase in the proportion of NMDAR-only synapses was prevented by metabotropic glutamate receptor antagonists. Notably, chronic NMDAR blockade incubation did not block the formation of the AMPAR EPSC, indicating that NMDAR-dependent plasticity is not necessary for the onset of AMPAR synaptic transmission in this system. We conclude that action potentials and ionotropic glutamate receptor activation are necessary for the developmental increase in AMPAR quantal size and that metabotropic glutamate receptor activation is required for the production of NMDAR-only synapses, but none of these is essential for synapse formation.

Distribution of alleles of the methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism in familial spina bifida

Spina bifida cystica (SB) is one of the most common and disabling of birth defects. Folic acid supplementation in mothers during the periconceptional period has been shown to prevent more than 70% of neural tube defects (NTD) including SB. However, the mechanism is unknown. We tested a series of multicase SB families in which 224 individuals were genotyped and a group of 215 unrelated unaffected (external) control individuals for association of SB with the T allele of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism that produces a heat-labile enzyme protein. The data were analyzed using first the transmission/disequilibrium test (TDT) and second a modified case-control study design with Monte Carlo sampling methods. No association of SB with the MTHFR T allele was found by either method. Presently, association between SB and the T allele has been found in four studies, a Dutch study, an Irish study, a North American study, and an Italian study. But no association was found in four other studies, a British study, a French study, a Turkish study, and a German study. A California population-based study found only modestly increased risk of SB with this allele that was not significant at the P < 0.05 level. The present study finds no evidence of the association. Only one other study, the German study, has used TDT analysis. The present study is the first to use a modified case-control study design with Monte Carlo sampling methods to test this association. Thus, it appears that the MTHFR T allele is a risk factor for SB in some populations but not others. Major genetic risk factors for folate-related SB remain to be found.

Lipoprotein lipase activity is stimulated by insulin and dexamethasone in cardiomyocytes from diabetic rats

Type 1 diabetes mellitus reduces lipoprotein lipase (LPL) activity in the heart. The diabetic phenotype of decreased LPL activity in freshly isolated cardiomyocytes persisted after overnight culture (16 h). Total cellular LPL activity was 311+/-56 nmol oleate released x h(-1) x mg(-1) cell protein in diabetic cultured cardiomyocytes compared with 661+/-81 nmol oleate released x h(-1) x mg(-1) cell protein for control cultured cells. Diabetes also resulted in lower heparin-releasable (HR) LPL activity compared with control cells (111+/-25 vs. 432+/-63 nmol x h(-1) x mg(-1) cell protein). In kinetic experiments, the reduction in total cellular LPL and HR-LPL activities in cultured cells from diabetic hearts was due to a decrease in maximal velocity, with no change in apparent Km for substrate (triolein). LPL activity in primary cultures of cardiomyocytes from control rats is stimulated by the combination of insulin (Ins) and dexamethasone (Dex). Overnight treatment of cultured cardiomyocytes from diabetic rats with Ins+Dex elicited an 84% increase in cellular LPL activity (to 572+/-65 nmol x h(-1) x mg(-1) cell protein) and a 194% increase in HR-LPL activity (to 326+/-46 nmol x h(-1) x mg(-1) cell protein). This stimulation occurred at subnanomolar concentrations of the hormones, but neither hormone was effective alone. The amount of immunoreactive LPL protein mass in cultured cardiomyocytes from diabetic hearts was unchanged by Ins+Dex treatment. Addition of oleic acid (60 microM) to the overnight culture medium inhibited the already reduced HR-LPL activity in diabetic cultured cells by 73% (to 30+/-4 nmol x h(-1) x mg(-1) cell protein). The presence of oleic acid also reduced hormone-stimulated HR-LPL activity. Increasing the glucose concentration in the culture medium to 26 mM had no effect on total cellular LPL or HR-LPL activities.

Myocardial adaptation to ischaemia--the preconditioning phenomenon

The phenomenon of ischaemic preconditioning, highlights a new and endogenous route to myocardial protection, which we believe could be exploited in our search for new therapeutic ways to protect the infarcting myocardium. Ischaemic preconditioning has been shown to be associated with both an early, or acute phase of protection lasting approximately 1-2 hours, as well as a delayed phase or "second window of protection" seen at least 24 hours following the initial sublethal ischaemic insult, and lasting up to 72 hours. We believe that both responses are triggered by similar receptor mediated events in addition to using the similar signalling pathways involving kinase cascades. However it is thought that the ultimate target or end-effector through which the protection is manifest may be different for the early vs. late effects. Some evidence exists that the end-effector involved in early preconditioning may be via the ATP-sensitive potassium channel (K(ATP)). With respect to the second window of protection, the cellular mechanisms underlying this are not fully understood at present, however we believe that they may be dependent upon a similar signalling transduction pathway with upregulation of cytoprotective proteins such as the heat stress proteins, and/or anti-oxidant proteins. Evidence demonstrating that preconditioning can occur in the human myocardium is also accumulating. In this respect cultured human ventricular myocytes as well as human atrial muscle have been shown to be preconditioned with brief episodes of simulated ischemia. These human preparations also respond to the known triggers and possible end-effectors of preconditioning, (e.g. adenosine receptor stimulation and K(ATP) channel opening) as well as being able to elicit their responses through the PKC signalling pathway. Further support for this phenomenon, in man, comes from PTCA studies demonstrating that this invasive procedure can put patients into a "preconditioned state"; this effect being associated with reduced ischaemic symptoms as well as the involvement of the adenosine receptor and K(ATP) channel. Of further interest is the observation that patients with a previous history of angina, prior to a MI, sustain smaller infarcts and have an improved survival. However the most direct evidence that preconditioning occurs in man comes from studies in patients undergoing coronary artery bypass surgery. The above evidence that preconditioning can occur in man makes it now possible to begin to design clinical studies investigating cardioprotective properties of drugs that can specifically mimic this phenomenon.

Characterization of gastrin-releasing peptide receptors aberrantly expressed by non-antral gastric adenocarcinomas

Epithelial cells lining the GI tract except in the gastric antrum do not normally express gastrin-releasing peptide receptors (GRP-R). Because GRP-R activation causes the proliferation of many GI cancer cell lines, aberrant expression has been presumed to negatively influence patient survival. We therefore determined the incidence and quality of GRP-R aberrantly expressed by non-antral gastric adenocarcinomas, and evaluated the impact of receptor expression on patient survival. We studied RNA isolated from 20 consecutive non-antral gastric adenocarcinomas, and determined that 8 (40%) aberrantly expressed GRP-R. Of these, 6 (75%) were found to be mutated. Pharmacologically, the effect of these mutations ranged from rendering the GRP-R non-functional to constitutively active. Contrary to expectations, however, survival of patients whose tumor expressed functional GRP-R (18.5 +/- 9.8 months) was not statistically different from those that did not (8.3 +/- 1.8 months; p = 0.24). Thus our data indicate that mutated isoforms of GRP-R are commonly expressed by non-antral gastric adenocarcinomas. However, expression of functional GRP-R does not alter patient survival, suggesting that this receptor may not be clinically important to the growth of gastric cancers.

Contribution of structural neuroimaging to the early diagnosis of Alzheimer's disease

There is compelling evidence for the early involvement of the hippocampal formation in the natural history of Alzheimer's disease (AD). The evidence comes from recent neuropathology, neuropsychology, and neuroimaging studies. AD-type histopathologic changes limited to the hippocampus have been described and may be seen in normal aging subjects. The sites of maximal neuronal loss in the hippocampal formation are in the CA1, subiculum, and entorhinal cortex. Minimally cognitively impaired (MCI) individuals (defined by ratings of functional capacity and psychiatric symptomatology) exhibit a neuropsychological profile that is distinct from that of the unimpaired elderly. Pathologic evidence suggests that most of these cases already have AD brain changes accentuated in the hippocampal region, and our own longitudinal studies reveal that 70% of this group develop dementia within a 4-year period. We have developed a negative-angle axial view designed to cut parallel to the anterior-posterior plane of the hippocampus. Using this modified axial plane of section in conjunction with computed tomography (CT) and magnetic resonance imaging (MRI), we estimated the prevalence of hippocampal atrophy in normal aging and across severity levels of cognitively impaired elderly patients. Longitudinal study shows that hippocampal atrophy is a sensitive and specific predictor of future AD for patients with MCI. MRI volume study of AD patients, controls, and MCI patients shows specific hippocampal volume loss in MCI. We conclude that the atrophic changes associated with early AD can be visualized using qualitative techniques and are readily quantifiable with volumetry. This article is not intended to be comprehensive, but to provide an overview of some of the structural neuroimaging data from our laboratory.

Incomplete processing of proinsulin to insulin accompanied by elevation of Des-31,32 proinsulin intermediates in islets of mice lacking active PC2

The prohormone convertases PC2 (SPC2) and PC3/PC1 (SPC3) are the major precursor processing endoproteases in a wide variety of neural and endocrine tissues. Both enzymes are normally expressed in the islet beta cells and participate in proinsulin processing. Recently we generated mice lacking active PC2 due to a disruption of the PC2 gene (Furuta, M., Yano, H., Zhou, A., Rouillé, Y., Holst, J. J., Carroll, R. J., Ravazzola, M., Orci, L., Furuta, H., and Steiner, D. F. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 6646-6651). Here we report that these PC2 mutant mice have elevated circulating proinsulin, comprising 60% of immunoreactive insulin-like components. Acid ethanol extractable proinsulin from pancreas is also significantly elevated, representing about 35% of total immunoreactive insulin-like components. These increased amounts of proinsulin are mainly stored in secretory granules, giving rise to an altered appearance on electron microscopy. In pulse-chase experiments, the mutant islets incorporate lesser amounts of isotopic amino acids into insulin-related components than normal islets. In both wild-type and mutant islets, proinsulin I was processed more rapidly to insulin, reflecting the preference of both PC2 and PC3 for substrates having a basic amino acid positioned four residues upstream of the cleavage site. The overall half-time for the conversion of proinsulin to insulin is increased approximately 3-fold in the mutant islets and is associated with a 4-5-fold greater elevation of des-31,32 proinsulin, an intermediate that is formed by the preferential cleavage of proinsulin at the B chain-C-peptide junction by PC3 and is C-terminally processed to remove Arg31 and Arg32 by carboxypeptidase E. The constitutive release of newly synthesized proinsulin from both mutant and wild-type islets during the first 1-2 h of chase was normal (<2% of total). These results demonstrate that PC2 plays an essential role in proinsulin processing in vivo, but is quantitatively less important in this regard than PC3, and that its absence does not influence the efficient sorting of proinsulin into the regulated secretory pathway.

Heparin-releasable lipoprotein lipase activity is increased in cardiomyocytes after culture

The activity of lipoprotein lipase (LPL) in adult rat heart cardiomyocytes after overnight culture on laminin-coated plates for 18-22 h was compared with enzyme activity in freshly isolated cardiomyocytes. LPL activity in cellular homogenates from cultured cardiomyocytes and freshly isolated cells was 240 and 233 nmol oleate released h-1.mg-1 protein, respectively. LPL specific activity (mU/ng LPL protein) was 0.07 in cultured cells compared with 0.42 in freshly isolated cells, indicating an increased content of inactive LPL mass after overnight culture. The heparin-induced release of LPL activity into the medium of cultured cardiomyocytes (198 nmol.h-1.mg-1) was much greater than heparin-releasable LPL (HR-LPL) activity (59 nmol.h-1.mg-1) from freshly isolated cells. HR-LPL activity from cultured cardiomyocytes was dependent on serum (16.3-fold activation) and was inhibited by high ionic strength (1 M NaCl) and by a polyclonal antibody to LPL. Cultured cardiomyocytes also had more immunodetectable LPL on the cell surface compared with freshly isolated cardiomyocytes, consistent with increased HR-LPL activity. Therefore, overnight culture may permit cardiomyocytes time to recover from the stress of isolation by increasing the content of LPL on the cell surface.

Effects of specimen collection, processing, and storage conditions on stability of human immunodeficiency virus type 1 RNA levels in plasma

To define the optimal blood collection parameters for plasma human immunodeficiency virus type 1 (HIV-1) viral load testing, plasma HIV-1 RNA levels were quantitated with the NASBA HIV-1 RNA QT System from blood specimens that were collected, processed, and stored under a variety of conditions that might have affected HIV-1 RNA stability. We determined that when whole blood was processed within 2 h of specimen collection the levels of HIV-1 RNA detected in EDTA-, heparin-, and acid citrate dextrose (ACD)-anticoagulated plasma samples were comparable. The levels of HIV-1 RNA in serum specimens (mean = 4.126 log units) were significantly lower (P < 0.01) than the levels in corresponding plasma samples (mean = 4.501 log units). One cycle of freeze-thaw (-70 degrees C) did not significantly reduce the level of HIV-1 RNA detected in EDTA-, heparin-, or ACD-anticoagulated plasmas. The EDTA-anticoagulated plasmas showed the smallest decrease in HIV-1 RNA copies (0.050 log units). HIV-1 RNA levels decreased over a 6-month time period in serum as well as in EDTA-, ACD-, and heparin-anticoagulated plasmas stored at -70 degrees C. However, the only significant decreases were for serum (mean decrease = 0.317 log units) and heparin-anticoagulated samples (mean decrease = 0.384 log units). A comparison of the levels of HIV-1 RNA in cell-free plasma collected in VACUTAINER EDTA Plasma Preparation Tubes and in standard VACUTAINER EDTA tubes determined that HIV-1 RNA levels were stable for up to 30 h after collection when stored at either room temperature (mean standard deviation [SD] = +/- 0.101 log units) or at 4 degrees C (mean SD = +/- 0.102 log units) as cell-free plasma or as EDTA-anticoagulated whole blood (mean SD = +/- 0.109 log units). These data indicate that EDTA-anticoagulated plasma is the most suitable and stable matrix for HIV-1 RNA quantitation.

Lipoprotein lipase activity in rat cardiomyocytes is stimulated by insulin and dexamethasone

Lipoprotein lipase (LPL) activity was studied in rat cardiomyocytes after overnight culture (16 h) in the presence of insulin (100 nM) and/or dexamethasone (100 nM). Insulin in combination with dexamethasone (INS/DEX) increased heparin-releasable LPL activity by 71% over the control level (566+/-85 versus 331+/-48 nmol/h.mg cell protein). This was accompanied by a 61% increase in total cellular LPL activity (914+/-89 versus 567+/-64 nmol/h.mg cell protein). The increase in LPL activity occurred at sub-nanomolar concentrations of the hormones, but neither hormone was effective alone. LPL protein mass, quantified by ELISA, was the same in both control and INS/DEX-treated cells (27.7 versus 28.6 ng/mg cell protein, respectively), thus LPL specific activity in cardiomyocytes was increased by INS/DEX treatment (0.113 versus 0.069 mU/ng LPL protein). These findings emphasize the importance of hormonal interactions in the regulation of LPL in heart tissue.

Fatty acids reduce heparin-releasable LPL activity in cultured cardiomyocytes from rat heart

Varying glucose and fatty acid (FA) concentrations in the medium of cultured cardiomyocytes from adult rat hearts were tested for effects on lipoprotein lipase (LPL) activity. Glucose (5.5, 11, and 25 mM in the culture medium for 18-22 h) had no effect on either heparin-releasable LPL (HR-LPL) or on cellular LPL (C-LPL) activities. When cardiomyocytes were cultured overnight with 60 microM oleate, HR-LPL activity was reduced to 20% of control, with no change in C-LPL activity or total C-LPL mass. Similar results (HR-LPL and C-LPL activities) were obtained with 60 microM concentrations of palmitate and myristate; linoleate and eicosapentaenoate did reduce C-LPL activity, but the decrease in HR-LPL activity was much greater. Oxfenicine, an FA oxidation inhibitor, did not alter the inhibitory effect of 60 microM oleate on HR-LPL. Short-term incubations (1 and 3 h) of cultured cardiomyocytes with 60 microM oleate did not displace LPL into the medium. Immunodetectable LPL on the cell surface of oleate-treated cultured cardiomyocytes was increased compared with control cells, but heparin treatment released the same amount of LPL mass that had reduced catalytic activity.

Defective prohormone processing and altered pancreatic islet morphology in mice lacking active SPC2

The prohormone convertase SPC2 (PC2) participates in the processing of proinsulin, proglucagon, and a variety of other neuroendocrine precursors, acting either alone or in conjunction with the structurally related dense-core granule convertase SPC3 (PC3/PC1). We have generated a strain of mice lacking active SPC2 by introducing the neomycin resistance gene (Neor) into the third exon of the mSPC2 gene. This gene insertion results in the synthesis of an exon 3-deleted form of SPC2 that does not undergo autoactivation and is not secreted. The homozygous mutant mice appear to be normal at birth. However, they exhibit a small decrease in rate of growth. They also have chronic fasting hypoglycemia and a reduced rise in blood glucose levels during an intraperitoneal glucose tolerance test, which is consistent with a deficiency of circulating glucagon. The processing of proglucagon, prosomatostatin, and proinsulin in the alpha, delta, and beta cells, respectively, of the pancreatic islets is severely impaired. The islets in mutant mice at 3 months of age show marked hyperplasia of alpha and delta cells and a relative diminution of beta cells. SPC2-defective mice offer many possibilities for further delineating neuroendocrine precursor processing mechanisms and for exploring more fully the physiological roles of many neuropeptides and peptide hormones.

The role of platelet-derived growth factor in intraluminal stented graft healing

BACKGROUND

Intraluminally placed polytetrafluoroethylene grafts are associated with enhanced graft endothelialization and diminished intimal hyperplasia when compared with interposition grafts. This study determined the role of platelet-derived growth factor in intraluminal graft healing.

STUDY DESIGN

Thirty dogs underwent infrarenal abdominal aorta polytetrafluoroethylene interposition (control, n = 15) or intraluminal stented (n = 15) grafting. Grafts were explanted at 1, 3, and 6 weeks. The percent of graft area endothelialization and intima to media height ratios were calculated. By using protein electrophoresis and the Western blot technique, platelet-derived growth factor, identified by immunolabeling with anti-platelet-derived growth factor antibody, was isolated from proximal, mid-, and distal graft regions and was quantified using densitometry.

RESULTS

Graft area endothelialization was 0 +/- 3.3 percent, 2.3 +/- 3.3 percent, and 19.0 +/- 3.3 percent for 1-, 3-, and 6-week controls; and 4.7 +/- 3.7 percent, 30.5 +/- 3.3 percent, and 86.8 +/- 3.3 percent for 1-, 3-, and 6-week stented grafts. Endothelialization was greater in stented grafts at 3 and 6 weeks (p < .01). Proximal anastomosis intima to media height ratios were 1.61 +/- 0.15, 1.54 +/- 0.14, and 1.48 +/- 0.15 for 1-, 3-, and 6-week control grafts, and 0.42 +/- 0.18, 0.41 +/- 0.15, and 0.47 +/- 0.14 for 1-, 3-, and 6-week stented grafts. Similar intima to media height ratio values were present at the distal anastomosis. Lower intima to media height ratios were observed in all stented grafts (p < .01). The platelet-derived growth factor content at 1-, 3-, and 6-weeks was lower in all stented grafts when compared with controls. The content of platelet-derived growth factor was greatest in 3-week controls, with a significant difference noted in the mid-graft region (p < .05). The content of platelet-derived growth factor remained stable in all stented graft regions over 6 weeks. An inverse correlation between stented graft platelet-derived growth factor content and endothelialization (r = -0.43) and a positive correlation with proximal anastomotic intimal hyperplasia (r = 0.73) were identified.

CONCLUSIONS

Lower platelet-derived growth factor content is associated with decreased intimal hyperplasia and improved healing in intra-arterial polytetrafluoroethylene grafts.

Differences in bereavement reactions within couples following death of a child

Differences in distress within couples who have experienced the sudden death of a child were examined. Results from two independent samples (N = 50 couples and N = 60 couples) were compared. The SCL-90-R and the BSI were used to measure global psychological distress and distress in nine symptom dimensions. Paired t tests revealed similar findings in the two samples: Within couples, women had significantly greater global distress than men and significantly greater distress than men in most symptom dimensions. Hostility scores within couples were similar and indicated a high level of hostility. The findings may explain relational problems observed within bereaved couples. Interventions designed to help couples cope with their differences and their hostility may decrease relational problems.

Fat and carbohydrate metabolism during exercise in elderly and young subjects

We evaluated the effect of aging on fat and carbohydrate metabolism during moderate intensity exercise. Glycerol, free fatty acid (FFA), and glucose rate of appearance (Ra) in plasma and substrate oxidation were determined during 60 min of cycle ergometer exercise in six elderly (73 +/- 2 yr) and six young adults (26 +/- 2 yr) matched by gender and lean body mass. The elderly group was studied during exercise performed at 56 +/- 3% of maximum oxygen uptake, whereas the young adults were studied during exercise performed at the same absolute and at a similar relative intensity as the elderly subjects. Mean fat oxidation during exercise was 25-35% lower in the elderly subjects than in the young adults exercising at either the same absolute or similar relative intensities (P < 0.05). Mean carbohydrate oxidation in the elderly group was 35% higher than the young adults exercising at the same absolute intensity (P < 0.001) but 40% lower than the young adults exercising at the same relative intensity (P < 0.001). Average FFA Ra in the elderly subjects was 85% higher than in the young adults exercising at the same absolute intensity (P < 0.05) but 35% lower than the young adults exercising at a similar relative intensity (P < 0.05). We conclude that fat oxidation is decreased while carbohydrate oxidation is increased during moderate intensity exercise in elderly men and women. The shift in substrate oxidation was caused by age-related changes in skeletal muscle respiratory capacity because lipolytic rates and FFA availability were not rate limiting in the older subjects.

Interaction of phosphorylated FcepsilonRIgamma immunoglobulin receptor tyrosine activation motif-based peptides with dual and single SH2 domains of p72syk. Assessment of binding parameters and real time binding kinetics

To examine the characteristics of the interaction of the FcepsilonRIgamma ITAM with the SH2 domains of p72(syk), the binding of an 125I-labeled dual phosphorylated FcepsilonRIgamma ITAM-based peptide to the p72(syk) SH2 domains was monitored utilizing a novel scintillation proximity based assay. The Kd for this interaction, determined from the saturation binding isotherm, was 1.4 nM. This high affinity binding was reflected in the rapid rate of association for the peptide binding to the SH2 domains. Competition studies utilizing a soluble C-terminal SH2 domain knockout and N-terminal SH2 domain knockouts revealed that both domains contribute cooperatively to the high affinity binding. Unlabeled dual phosphorylated peptide competed with the 125I-labeled peptide for binding to the dual p72(syk) SH2 domains with an IC50 value of 4.8 nM. Monophosphorylated 24-mer FcepsilonRIgamma ITAM peptides, and phosphotyrosine also competed for binding, but with substantially higher IC50 values. This, and other data discussed, suggest that high affinity binding requires both tyrosine residues to be phosphorylated and that the preferred binding orientation of the ITAM is such that the N-terminal phosphotyrosine occupies the C-terminal SH2 domain and the C-terminal phosphotyrosine occupies the N-terminal SH2 domain.

Gastric metaplasia and duodenal ulcer disease in children infected by Helicobacter pylori

BACKGROUND

Helicobacter pylori infection of the gastric mucosa is vital in the pathogenesis of duodenal ulcer disease. H pylori will only colonise gastric epithelium and its association with duodenal disease is therefore not easily explained.

AIMS

To determine if gastric metaplasia in the duodenum increases the risk of duodenal ulcer disease in children infected with H pylori.

PATIENTS

All children undergoing upper endoscopy over a 20 month period in a children's hospital in Ireland.

METHODS

Two biopsy specimens were obtained from the antral mucosa and two from the first part of the duodenum. One antral biopsy specimen was used in a rapid urease test (Clo Test). Biopsy sections were stained with haematoxylin and eosin and also with cresyl violet for identification of H pylori. Periodic acid Schiff (PAS) stain was performed to identify areas of gastric metaplasia.

RESULTS

Gastric and duodenal biopsy specimens were obtained from 148 patients (M:F 1:2:1). Twenty five children (17%) had H pylori positive gastritis. Thirty four children (23%) had gastric metaplasia in the duodenum. Nine per cent of children under the age of 8 years had gastric metaplasia compared with 38% in those 12 years of age or over (p < 0.005). Seven children had duodenal ulcer disease. Gastric metaplasia was present in six of seven (86%) children with duodenal ulcer disease compared with 28 of 141 (20%) without ulceration (p < 0.001). While both H pylori and gastric metaplasia were each significant risk factors for duodenal ulcer disease, the combined presence of both factors was associated with a pronounced increase in duodenal ulcer disease. Duodenal ulcer disease occurred in over 50% of children with both H pylori infection and gastric metaplasia. In contrast duodenal disease did not occur in children (0 of 100) when both were absent.

CONCLUSION

The presence of gastric metaplasia in the duodenum is the major risk factor for duodenal ulcer disease in patients colonised by H pylori.

The role of prohormone convertases in insulin biosynthesis: evidence for inherited defects in their action in man and experimental animals

The hormone insulin remains the cornerstone of diabetic therapy since it is required for almost all cases of Type 1 and many cases of Type 2 diabetes. Since the discovery of insulin in 1921, much has been learned about its chemistry, structure and action as well as its production in the beta cell. Insulin is formed through a series of precursors, beginning with preproinsulin, the protein encoded in the insulin gene. These precursors direct the prohormone into the secretory pathway and ultimately into the secretory granules where it is converted into insulin and C-peptide. These products are stored and secreted together in a highly regulated manner in response to glucose and other stimuli. This review focuses on the recently discovered prohormone convertases, PC2 and PC3 (PC1), the enzymes responsible for the endoproteolytic processing of proinsulin to insulin and C-peptide in the beta cell as well as for the selective processing of proglucagon to glucagon in the alpha cell or GLP1 in intestinal L-cells. PC2 and PC3 are calcium-dependent serine proteases related to the bacterial enzyme subtilisin. They cleave selectively at Lys-Arg or Arg-Arg sites in precursors, generating products with C-terminal basic residues that are then removed by carboxypeptidase E, an exopeptidase. All 3 enzymes are expressed mainly in secretory granules of neuroendocrine cells throughout the body and in the brain. Inherited defects affecting the prohormone-processing enzymes have recently been found in association with unusual syndromes of obesity and other metabolic disorders.

The molecular biology of hormone and growth factor receptors in meningiomas

Expression of a number of steroid hormone and growth factor receptors is characteristic of meningiomas. This paper reviews the analysis of receptors for progesterone, estrogen, androgen and platelet derived growth factor (PDGF) in human meningioma tissue specimens. Progesterone receptor was assessed by Northern blot analysis and immunohistochemistry in meningioma tissue specimens. Progesterone receptor mRNA was expressed in 64% of the meningiomas examined. Immunohistochemical data correlated well with the Northern blot analysis. The staining was clearly nuclear. Expression was more common in meningioma tissue from women than from men. Analysis of receptor expression in tissue culture derived from meningioma specimens demonstrated the loss of progesterone receptor within one to two passages. It was shown that the progesterone receptor mRNA expression which is present in meningiomas is functional by transfection techniques. The estrogen receptor was undetectable by Northern blot analysis; a small amount could be detected in meningioma tissue specimens by polymerase chain reaction (PCR). The androgen receptor was found in 67% of the specimens examined. Like the progesterone receptor, it was more common in women than in men (69% vs. 31%). The immunohistochemical data correlated well with the Northern blot analysis, with the receptor predominantly found in the nucleus. Unlike progesterone receptor, androgen receptor expression was not lost in cell culture. The subunits for PDGF were expressed in various quantities in meningiomas. Only the PDGF beta-receptor (PDGFR-beta) not alpha-receptor, was found in meningioma tissue specimens. In contrast, the ligands PDGF A and PDGF B were expressed in all tumors. The functionality of the PDGF beta-R was determined by examining the induction of the protooncogene C-fos by PDGF BB in meningioma cell cultures. A significant increase in C-fos protein was observed with the addition of PDGF BB to meningioma cultures.

Expression of platelet-derived growth factor transcripts in medulloblastomas and ependymomas

We used Northern blot analysis to measure the expression of mRNA for platelet-derived growth factor subunit A (PDGF-A), PDGF-B and the PDGF-alpha receptor (PDGFR-alpha) and PDGF-beta receptor (PDGFR-beta) in ependymomas and medulloblastomas. We analyzed tissue from 5 patients for each tumor type, looking specifically for components of an autocrine or paracrine system in these tumors. PDGF-A was expressed in all tumors, PDGFR-alpha, which binds all 3 PDGF isoforms, was only found in ependymomas. Thus only ependymomas appeared to have a potential for using PDGFR-alpha autocrine loops. PDGF-B was expressed only in ependymomas, although the PDGFR-beta was expressed in both medulloblastomas and ependymomas. Again, therefore, only ependymomas appear to have a potential autocrine loop with PDGFR-beta. These data suggest that ependymomas have the biochemical prerequisites for autocrine and/or paracrine loops using PDGFR-alpha or PDGFR-beta systems. In this they resemble other glial tumors such as anaplastic astrocytomas and glioblastomas. Medulloblastomas do not appear to have the ligand and/or receptor for either the PDGFR-alpha or PDGFR-beta autocrine loop.

Radiotherapy alone compared with radiotherapy and chemotherapy in patients with squamous cell carcinoma of the esophagus

PURPOSE

The purpose of this study is to determine whether primary treatment with both radiotherapy and chemotherapy is superior to radiotherapy alone in patients with squamous cell carcinoma of the esophagus.

PATIENTS AND METHODS

From January 1980 to December 1988, 77 patients from two Veterans Affairs hospitals with clinically staged nonmetastatic squamous cell carcinoma of the esophagus received either radiotherapy alone (RT group) or concomitant radiotherapy and chemotherapy (RT + CT group) with curative intent. Each group originated at a different hospital, but all patients were irradiated in the same radiotherapy department. Chemotherapy consisted of cisplatin and 5-fluorouracil. Forty-two patients received RT alone, and 35 received RT + CT. Locoregional control, disease-free survival, and overall survival rates were compared.

RESULTS

Locoregional control, disease-free survival, and overall survival rates were significantly higher in the RT + CT group when compared to RT group, 26% vs 5%, 20%, vs 2%, and 29% vs 7%, respectively, at 2 years (P = .01, 0.02 and 0.02, respectively). The median survival was 14 months for the RT + CT group and 7.5 months for the RT group. There was no difference in the incidence of distant metastases except for bone metastases. No one in the RT + CT group developed bone metastases compared to nine patients in the RT group (P = .01).

CONCLUSION

This retrospective analysis shows improved locoregional control, disease-free survival, and survival when chemotherapy consisting of cisplatin and 5-FU is given in addition to radiation for patients with squamous cell carcinoma of the esophagus. Bony metastases were absent in those who received chemotherapy.

"Best-of-breed" vs. monolithic solutions. Roundtable discussion

The debate is hotter now than it was when we alluded to it in our June issue's "round table." CIOs and IS directors still wonder about the strategic advantages of single-vendor solutions vs. the best-of-breed approach. In June we noted that this dynamic has driven system acquisitions for several years. Since then we have witnessed what amounts to a feeding frenzy. We asked a few experts to discuss their perceptions of the controversy. Their comments follow.

Post-transcriptional mechanisms are responsible for the reduction in lipoprotein lipase activity in cardiomyocytes from diabetic rat hearts

Lipoprotein lipase (LPL) activity is reduced in cardiomyocytes from rat hearts following the acute (4-5 day) induction of diabetes with 100 mg/kg streptozotocin. The molecular basis for this inhibitory effect of diabetes on LPL activity was investigated by measuring steady-state LPL mRNA content and the synthesis and turnover of LPL protein ([35S]methionine incorporation into immunoprecipitable LPL protein in pulse and pulse-chase experiments) in control and diabetic cardiomyocytes. LPL activity was reduced to approx. 50% of control in diabetic cardiomyocytes, but LPL mRNA levels and turnover (degradation) of newly synthesized LPL were unchanged. Synthesis of total protein and LPL were reduced to 72% and 71% of control respectively; therefore, relative rates of LPL synthesis were the same in control and diabetic cardiomyocytes. The diabetes-induced reduction in LPL synthesis was accompanied by a decrease in LPL mass to 78% of control, and a decrease in enzyme specific activity (0.48 to 0.33 m-unit/ng of LPL protein) since the decline in catalytic activity was greater than the decrease in LPL synthesis and mass. Thus, post-transcriptional mechanisms involving a reduction in LPL synthesis as part of a generalized decrease in total protein synthesis, together with a post-translational mechanism(s) that result in accumulation of inactive LPL protein, are responsible for the decreased LPL activity in cardiomyocytes from diabetic rat hearts.

Does a sodium-free buffer affect QRS width in experimental amitriptyline overdose?

STUDY OBJECTIVES

We carried out this study to determine the effects of pH alteration on QRS width with administration of tromethamine, a non-sodium-containing buffering agent, in experimental amitriptyline overdose.

DESIGN

Prospective, nonblinded trial.

PARTICIPANTS

Adult mongrel dogs.

INTERVENTIONS

Pentobarbital-anesthetized dogs were overdosed with amitriptyline 5 mg/kg followed by infusion at 1.0 mg/kg/minute until the QRS width doubled, then decreased to .5 mg/kg/minute until the end of the experiment. At two defined points of toxicity, the dose of tromethamine required to raise the pH to 7.50 +/- 4 was given. pH and QRS width at a speed of 100 mm/second were measured over a 30-minute period after each tromethamine dose. Data were analyzed with non-linear-regression analysis.

RESULTS

At toxicity 1 the mean pH was 7.32, with a QRS width of 11.6 mm. Two minutes after the tromethamine dose the pH rose to 7.51, with narrowing of the QRS width to 8.4 mm. At toxicity 2 the pH was 7.40, with QRS width of 10.6 mm. Two minutes after tromethamine, the pH rose to 7.49 and the QRS width decreased to 9.7 mm. Regression analysis showed a correlation between pH and QRS width; as pH increased, QRS width decreased (P = .0001).

CONCLUSION

Cardiac toxicity of amitriptyline overdose, as manifested by QRS widening, is reversible by pH changes alone.

Amyloid formation in response to beta cell stress occurs in vitro, but not in vivo, in islets of transgenic mice expressing human islet amyloid polypeptide

BACKGROUND

Human, but not mouse, islet amyloid polypeptide (IAPP) is amyloidogenic. Transgenic mice overexpressing human IAPP in the beta cells of the islets of Langerhans should be useful in identifying factors important for the deposition of IAPP as insoluble amyloid fibrils.

MATERIALS AND METHODS

Transgenic mice expressing human IAPP were examined using several experimental models for the production of persistent hyperglycemia, as well as for the overstimulation and/or inhibition of beta cell secretion. Obesity was induced by aurothioglucose. Persistent hyperglycemia was produced by long-term administration of glucocorticosteroids or by partial pancreatectomy. Inhibition of normal beta cell exocytosis by diazoxide administration, with or without concurrent dexamethasone injections, was carried out to increase crinophagy of secretory granules. The human IAPP gene was also introduced into the ab and ob mouse models for diabetes. Finally, isolated islets cultivated in vitro at high glucose concentration were also examined.

RESULTS

No amyloid deposits were found in the pancreata of any of the animals, either by light microscopy after Congo red staining or by electron microscopy after immunogold labeling with antibodies specific for human IAPP. Aurothioglucose treatment resulted in increased numbers of granules in the beta cell and the appearance of large lysosomal bodies without amyloid. However, islets from db and ob mice expressing human IAPP cultivated in vitro in the presence of glucocorticosteroid and/or growth hormone, were found to contain extracellular amyloid deposits reacting with antibodies to human IAPP.

CONCLUSIONS

Oversecretion of human IAPP or increased crinophagy are not sufficient for amyloid formation. This indicates that other factors must influence amyloid deposition; one such factor may be the local clearance of IAPP.

Comparative stabilities of quantitative human immunodeficiency virus RNA in plasma from samples collected in VACUTAINER CPT, VACUTAINER PPT, and standard VACUTAINER tubes

This study compared the levels of human immunodeficiency virus (HIV) virion RNA in plasma from whole blood collected in VACUTAINER CPT (cell preparation tube), VACUTAINER PPT (plasma preparation tube), VACUTAINER SST (serum separation tube), and standard VACUTAINER tubes with sodium heparin, acid citrate dextrose, sodium citrate, and potassium EDTA used as anticoagulants. Quantitative plasma HIV RNA levels were measured by branched-DNA signal amplification. Blood from all tubes was either processed within 1 to 3 h after collection or stored at room temperature or at 4 degrees C for analysis at 6 to 8 and 30 h postdraw. Immediately separated plasma from sodium citrate CPT tubes held at 4 degrees C maintained better stability of HIV RNA equivalents than whole blood held at room temperature or 4 degrees C. The highest number of HIV RNA equivalents was seen with EDTA VACUTAINER tubes. HIV RNA equivalents in all types of plasma were significantly higher than in SST tubes. Although a decline in HIV RNA equivalents was seen in all collection devices after 30 h, a significantly greater decline in plasma HIV RNA equivalents occurred in acid citrate dextrose VACUTAINER tubes than in citrate CPT, PPT, and standard EDTA VACUTAINER tubes. In order to minimize the variability of quantitative HIV RNA test results, our data suggest that samples collected for a particular assay should be processed at the same time postdraw using a particular tube type throughout a given study.

Expression of platelet derived growth factor and platelet derived growth factor receptor mRNA in a glioblastoma from a patient with Li-Fraumeni syndrome

Expression of platelet derived growth factor (PDGF) and PDGF-receptor mRNA was examined from a glioblastoma taken from a patient with Li-Fraumeni syndrome. Northern blot analysis and in situ hybridisation showed very high concentrations of both PDGF-A and PDGF alpha-receptor mRNA in the tumour. The overall pattern of PDGF expression was similar to those found in sporadic glioblastomas. Mutations in p53 has been implicated as an early pathogenic event leading to sporadic low grade astrocytomas, and is the third most common tumour type in patients with Li-Fraumeni syndrome, where they are predisposed due to a germline mutation in the p53 tumour suppressor gene. This study suggests that progression towards a glioblastoma in both the general population and in patients with Li-Fraumeni syndrome may involve potential autocrine and paracrine stimulation by growth factors such as PDGF.

Treatment of verapamil overdose with glucagon in dogs

STUDY OBJECTIVE

The purpose of this study was to evaluate the effectiveness of glucagon as a treatment for the hemodynamic effects of verapamil overdose in a canine model.

DESIGN

The study was performed in a nonblinded, controlled animal model.

INTERVENTIONS

Pentobarbital-anesthetized and instrumented dogs were maintained and observed for 60 minutes or until death. All animals were overdosed with 15 mg/kg i.v. verapamil over 30 minutes. Mean arterial pressure, heart rate, ECG, and cardiac output were monitored. The experimental group received a 2.5 mg glucagon i.v. bolus followed by a glucagon drip at 2.5 mg/hr. The control group received an equal volume of i.v. normal saline solution in the same fashion. Analysis was performed with the Dunnett and Tukey-Kramer methods, with alpha set at .05.

RESULTS

There were eight experimental and seven control animals, with mortality rates of 0% and 29%, respectively. The experimental group had increases in cardiac output and heart rate that were statistically significant at 45 and 60 minutes compared with those of the control group. In addition, there was a significant difference in heart rate at 30 minutes. No difference was noted between the groups for mean arterial pressure.

CONCLUSION

Glucagon appears to reverse both the bradycardia and the depressed cardiac output associated with verapamil overdose in a canine model.

Regulation by glucose of the biosynthesis of PC2, PC3 and proinsulin in (ob/ob) mouse islets of Langerhans

The prohormone convertases PC2 and PC3 have been shown to catalyze the processing of proinsulin to insulin in pancreatic beta-cells. In these studies we have compared the effects of glucose on PC2 and PC3 biosynthesis in freshly isolated islets from normal and hyperglycemic (ob/ob) mice. In contrast to normal islets [Alarcón, et al. (1993) J. Biol. Chem. 268, 4276] the biosynthesis of both PC2 and PC3 is stimulated by glucose, parallel to the stimulation of proinsulin in the (ob/ob) islets. Inhibition of PC2 biosynthesis by glucose in normal islet non beta-cells may obscure stimulation of PC2 biosynthesis in normal islet beta-cells.

Cross-linking of a B25 azidophenylalanine insulin derivative to the carboxyl-terminal region of the alpha-subunit of the insulin receptor. Identification of a new insulin-binding domain in the insulin receptor

To identify a site within the insulin receptor ectodomain which forms a binding pocket for B25 Phe and is responsible for initiating conformational changes required for high affinity binding of insulin we have used a novel photoreactive insulin, despentapeptide-(B26-B30) [B25 p-azidophenylalanine-alpha-carboxamide] insulin (APC insulin). This derivative has a highly photoreactive azido group incorporated into the aromatic ring of the B25 phenylalanine amide. APC insulin bound to human insulin receptors overexpressed on a transfected Chinese hamster ovary cell line (P3-A) with an apparent potency of 9-fold relative to that of native insulin and stimulated lipogenesis in rat adipocytes with an average potency equal to porcine insulin. Addition of biotin to the B1 Phe amino group to form despentapeptide-(B26-B30) [B1 (6-biotinylamidocaproyl)phenylalanine B25 p-azidophenylalanine-alpha-carboxamide] insulin derivative (Bio-APC insulin) did not adversely affect receptor-binding affinity and provided a convenient ligand for purification of cross-linked complexes. The efficiency of receptor cross-linking with these reagents was high (70%). To identify the site(s) of cross-linking, the insulin receptor in P3-A cells was first metabolically labeled with various individual 3H-labeled amino acids and then photoaffinity labeled with 125I-Bio-APC insulin, isolated, and digested with Lys-C endoproteinase. The resulting cross-linked peptide fragments were separated by streptavidin-affinity chromatography and sequenced. The smallest identified fragment comprised residues 704-718 of the COOH terminus of the alpha-subunit of the insulin receptor. This B25 Phe cross-linked region of the alpha-subunit lies just upstream of the Exon 11-encoded 12-amino acid COOH-terminal region. Aromatic residues in this predicted alpha-helical region may form a binding pocket for B25 Phe to initiate conformational changes required for stabilizing the high affinity binding state.

Stabilities of quantitative plasma culture for human immunodeficiency virus, RNA, and p24 antigen from samples collected in VACUTAINER CPT and standard VACUTAINER tubes

We evaluated the stability of human immunodeficiency virus (HIV) load markers from blood samples collected in VACUTAINER CPT or standard VACUTAINER brand tubes using sodium heparin or sodium citrate as anticoagulants. Quantitative plasma culture and p24 antigen concentrations were determined, and HIV RNA levels in plasma were measured by both reverse transcription-PCR-enzyme-linked immunosorbent assay (RT-PCR-ELISA) and branched DNA methods. All tubes were stored at room temperature for analysis at 2, 24, 48, and 72 h after the blood samples were drawn. No difference was seen between tube types with respect to the HIV titer in plasma or the positivity rate for all samples that demonstrated a fall in titer over time. Unbound p24 antigen levels in plasma decreased during the initial 48-h period in both tube types. Immune complex-dissociated p24 antigen levels decreased in CPT tubes but not in standard VACUTAINER tubes. The HIV RNA copy number in plasma measured by RT-PCR-ELISA was stable in most subjects and was significantly higher in CPT tubes than in standard VACUTAINER tubes at 24 and 72 h after the blood samples were drawn. The branched DNA probe assay detected a significant decline in HIV RNA equivalent in plasma over 72 h in both collection tubes, the decline being more dramatic in the standard VACUTAINER tube than the CPT tube. Overall, interday variability suggests that samples collected for a particular assay should be processed at the same time after blood is drawn and that a particular tube type be used throughout a given study.

A human immunodeficiency virus type 1 (HIV-1)-based retroviral vector system utilizing stable HIV-1 packaging cell lines

We have constructed stable human immunodeficiency virus (HIV) packaging cell lines that when transfected with an HIV-based retroviral vector produce packaged vectors capable of transducing susceptible CD4+ cells. This HIV-1-based retroviral vector system has the potential for providing targeted delivery and regulated expression of immunogens or antiviral agents in CD4+ cells.

Platelet-derived growth factor expression and stimulation in human meningiomas

The platelet-derived growth factor (PDGF) family consists of subunits A and B and receptors alpha and beta. This paper evaluates the potential role of the homodimer PDGF-BB as a growth factor in meningiomas. It analyzes the expression of messenger RNA in members of the PDGF family in these tumors, measures the growth response of meningiomas to exogenous PDGF-BB in culture, and examines the induction of the c-fos proto-oncogene by PDGF-BB. Northern blot analysis was carried out on tissue from 20 meningiomas to measure the expression of PDGF-A, PDGF-B, PDGF-alpha receptor (PDGF-alpha-R) and PDGF-beta receptor (PDGF-beta-R). All tumors expressed PDGF-A and PDGF-B subunits. Nineteen of the 20 tumors expressed PDGF-beta-R and none expressed PDGF-alpha-R as measured by this technique. Because the beta receptor is selectively sensitive to stimulation by the PDGF-B subunit, these data suggest that meningiomas might be susceptible to stimulation by PDGF-BB. To test this hypothesis, the effect of exogenous PDGF-BB on meningioma growth was evaluated by incubating cells from 10 human meningiomas. Tritiated thymidine incorporation was used to evaluate stimulation of growth over a 48-hour period using PDGF-BB concentrations of 1, 3, or 6 ng/ml. Linear regression analysis and multiple-factor analysis of variance were used to measure PDGF-BB effects. Three of the 10 tumor specimens responded significantly to PDGF-BB, with a three- to sixfold increase in thymidine incorporation over 72 hours of exposure, and there was a significant overall growth-stimulating effect of PDGF-BB in the 10 tumor specimens tested. In the last set of experiments, the functionality of the PDGF-beta-R was determined by examining the induction of the proto-oncogene c-fos by PDGF-BB in meningioma cell cultures. A significant increase in c-fos protein was observed 3 hours after PDGF-BB addition. These findings demonstrate that PDGF-A, PDGF-B, and PDGF-beta-R are expressed in meningiomas and suggest that the beta receptor is functional: when it is activated, c-fos levels are increased, and an increase in meningioma cell division is observed after the addition of PDGF-BB. These studies support the hypothesis that PDGF acts as a growth factor in meningiomas.

Effect of oral magnesium supplementation on selected cardiovascular risk factors in non-insulin-dependent diabetics

OBJECTIVE

To evaluate the impact of oral magnesium supplementation on risk factors for end-organ disease in patients with non-insulin-dependent diabetes mellitus (NIDDM).

DESIGN

A 16-week randomized, double-blind, placebo-controlled crossover trial.

SETTING

Outpatient center of an academic family medicine residency program.

PATIENTS

Twenty-eight patients (age range, 28 to 84 years; 57.1% black; 85.7% women) with NIDDM controlled by diet and/or an oral hypoglycemic, with a serum cholesterol levels over 5.20 mmol/L (200 mg/dL).

INTERVENTION

Following a 2-week placebo run-in period, each patient was randomized to receive either sustained-release magnesium chloride (Slo-Mag), 384 mg/d, or an identical-appearing placebo for 6 weeks. After a 2-week interim washout period, each patient was then treated with the alternative regimen for an additional 6-week period.

MAIN OUTCOME MEASURES

The systolic and diastolic blood pressure and levels of serum glucose, low-density and high-density lipoprotein and total cholesterol, triglycerides, and serum and total erythrocyte magnesium were measured at the beginning, midpoint, and end of each 6-week treatment phase.

RESULTS

Systolic blood pressure fell an average of 7.4 mm Hg (P < .05) with treatment. There was no significant change in diastolic blood pressure or levels of serum glucose, low-density and high-density lipoprotein and total cholesterol, triglycerides, or serum and erythrocyte magnesium.

CONCLUSIONS

Oral magnesium supplementation in the doses and duration studied is modestly effective in reducing systolic blood pressure in patients with NIDDM but has little impact on other important biochemical parameters related to diabetes-associated end-organ disease.