Sex differences in insulin levels in older adults and the effect of body size, estrogen replacement therapy, and glucose tolerance status. The Rancho Bernardo Study, 1984-1987

OBJECTIVE--To determine if insulin levels vary with sex, independent of estrogen replacement therapy (ERT), differences in body mass index (BMI), waist-to-hip ratio (WHR), and glycemia. RESEARCH DESIGN AND METHODS--In a population-based study of older adults, insulin levels were measured before and after a standardized oral glucose tolerance test in 673 men and 849 women, all free of known diabetes. RESULTS--Age-adjusted fasting insulin levels were highest in men, intermediate in women not taking estrogen, and lowest in estrogen-treated women (P < 0.01). Differences between men and women not taking estrogen disappeared after adjusting for age and BMI, but not glycemia; estrogen-treated women had significantly lower fasting insulin levels than did men (P < 0.01) and women not taking estrogen (P < 0.01). The association of estrogen use with lower fasting insulin levels persisted after adjusting for age and WHR (P < 0.001) and was stronger among women with abnormal glucose tolerance. Age-adjusted postchallenge insulin levels were higher in women than in men (P < 0.01). The sex difference persisted after adjusting for age and BMI or glycemia. Postchallenge insulin levels did not vary by ERT. CONCLUSIONS--Men have higher fasting insulin levels than do women, whether or not the women are using ERT. Differences between men and untreated women are explained by differences in BMI, but estrogen users have lower fasting insulin levels independent of BMI. Postchallenge insulin levels are higher in women than men and are independent of ERT, BMI, and glycemia. Clinical trials in women are needed to determine whether ERT can improve insulin and glucose metabolism.     

Subretinal neovascularization developing after prophylactic argon laser photocoagulation of atrophic macular scars

Twenty-eight anemic control dogs were subjected to isolated cerebral hypoxemic (PO2,35+/-5 mm Hg) perfusion for 2 hours. All were found to have functional pulmonary impairment. Two hours later, twenty were sacrificed and found to have the bilateral anatomic complex of the respiratory distress syndrome (RDS). All those not sacrificed expired within 20 hours with progressive respiratory distress and at autopsy had the bilateral anatomic complex. Twenty-three beagles with chronic denervation (autotransplantation) of the left lung also were subjected to the 2 hour isolated cerebral arterial hypoxemic perfusion. Minimal pulmonary functional impairment was measurable in all. Ten of sixteen were long-term survivors. The six that succumbed did not appear to suffer respiratory deaths. These six, as well as seven sacrificed 2 hours after perfusion, had the anatomic complex of RDS in the normally innervated right lungs. However, the denervated left lungs were anatomically normal. These findings are offered as additional evidence that RDS has a centrineurogenic etiology. We postulate the following sequence: "shock" causes cerebral (probably hypothalamic) cellular oxygen deprivation and dysfunction; there is autonomically mediated, increased resistance of the pulmonary venules ("postcapillary sphincters"); this leads to capillary hypertension, congestion, hemorrhage, edema, surfactant inactivation, and atelectasis. Pulmonary denervation blocks this sequence and protects the lung.     

Aromatic analogs of arcaine inhibit MK-801 binding to the NMDA receptor

Aromatic analogs of arcaine were shown to have inhibitory effects on the binding of the channel blocking drug [3H]MK-801 to the NMDA receptor complex. The most potent compound of the series was an N,N'-bis(propyl)guanidinium which inhibited [3H]MK-801 binding with an IC50 of 0.58 microM and an IC50 of 12.17 microM upon addition of 100 microM spermidine. The increase in IC50 upon addition of spermidine suggests competitive antagonism between the inhibitor and spermidine at the arcaine-sensitive polyamine site of the NMDA receptor complex.     

Mapping, genomic organization and promoter analysis of the human prostate-specific membrane antigen gene

Prostate-specific membrane antigen (PSMA) is a 100 kDa type II transmembrane protein with folate hydrolase and NAALAdase activity. PSMA is highly expressed in prostate cancer and the vasculature of most solid tumors, and is currently the target of a number of diagnostic and therapeutic strategies. PSMA is also expressed in the brain, and is involved in conversion of the major neurotransmitter NAAG (N-acetyl-aspartyl glutamate) to NAA and free glutamate, the levels of which are disrupted in several neurological disorders including multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease and schizophrenia. To facilitate analysis of the role of PSMA in carcinoma we have determined the structural organization of the gene. The gene consists of 19 exons spanning approximately 60 kb of genomic DNA. A 1244 nt portion of the 5' region of the PSMA gene was able to drive the firefly luciferase reporter gene in prostate but not breast-derived cell lines. We have mapped the gene encoding PSMA to 11p11-p12, however a gene homologous, but not identical, to PSMA exists on chromosome 11q14. Analysis of sequence differences between non-coding regions of the two genes suggests duplication and divergence occurred 22 million years ago.     

Notochordal cells interact with nucleus pulposus cells: regulation of proteoglycan synthesis

Normal erythrocytes are under physiological conditions characterized by low cation and high anion conductance. However, in the case of sickle cell anemia the erythrocytes contain a modified haemoglobin, HbS, which under low oxygen tension gives rise to sickling. This condition is preceded by an increase in cation conductance, especially due to the Ca2+-activated K+-channels, leading to net-efflux of KCI and thereby decreased cellular volume, which is part of the pathological condition.A possible symptomatic treatment could be application of conductance blockers, targeting the Ca2+-activated K+-channel or the anion conductance in order to minimize the passive transport of ions and solvent. It has been argued, that due to the high anion conductance, solute loss depended at moderately increased cation conductances on the cation only. Consequently the Ca2+-activated K+-conductance should be the target for attempts to modify solute loss.It is shown that: knowledge of mean conductances (time averages) for pathways showing fluctuations are insufficient to predict the quantitative effect of conductance inhibitors, since inhibition is strongly dependent on the kinetics of the mechanisms mediating the translocation and a block of the high conductance anion pathway can be as effective as inhibition of the Ca+-activated K+-conductance with regard to net salt loss.     

Activation of neurotrophin-3 receptor TrkC induces apoptosis in medulloblastomas

Elevated expression of the neurotrophin-3 (NT-3) receptor TrkC by childhood medulloblastomas is associated with favorable clinical outcome. Here, we provide evidence that TrkC is more than simply a passive marker of prognosis. We demonstrate that: (a) medulloblastomas undergo apoptosis in vitro when grown in the presence of NT-3; (b) overexpression of TrkC inhibits the growth of intracerebral xenografts of a medulloblastoma cell line in nude mice; and (c) trkC expression by individual tumor cells is highly correlated with apoptosis within primary medulloblastoma biopsy specimens. TrkC-mediated NT-3 signaling promotes apoptosis by activating multiple parallel signaling pathways and by inducing immediate-early gene expression of both c-jun and c-fos. Considered collectively, these results support the conclusion that the biological actions of TrkC activation affect medulloblastoma outcome by inhibiting tumor growth through the promotion of apoptosis.     

Simultaneous protection of G156A methylguanine DNA methyltransferase gene-transduced hematopoietic progenitors and sensitization of tumor cells using O6-benzylguanine and temozolomide

OBJECTIVE: To describe the clinical and radiologic features of superficial siderosis of the CNS after treatment of a cerebellar tumor. METHODS: Clinical assessment and MRI in four patients with superficial siderosis were performed. RESULTS: Four patients with superficial siderosis had been treated for a primary cerebellar tumor (astrocytoma in three patients, medulloblastoma in one patient) during childhood. All patients were treated with surgery and three received radiotherapy. Slowly progressive bilateral sensorineural hearing loss, gait ataxia, and limb ataxia appeared 8 to 22 years after diagnosis of the cerebellar tumor. Other clinical features were mild cognitive impairment, dysarthria, nystagmus, optic neuropathy, anosmia, and upper motor neuron signs. The CSF contained erythrocytes and increased protein. MRI with fast spin-echo T2-weighted and gradient-echo T2* sequences showed a hypointense rim of iron coating the surface of the cerebellum and brainstem. Twenty-one other patients who had survived more than 5 years after treatment of a primary cerebellar tumor did not have symptoms or signs suggestive of superficial siderosis. CONCLUSIONS: Superficial siderosis is an uncommon late complication of the treatment of a childhood cerebellar tumor, but it is probably underrecognized. The diagnosis should be suspected in patients who present with slowly progressive sensorineural hearing loss and ataxia many years after eradication of a childhood cerebellar tumor.     

A Comment on Ridge Regression. Biased Estimation for Non-Orthogonal Problems

In a recent issue of Technometrics, Hoer1 and Kennard [l] presented a comprehensive discussion of the problem of biased estimation in multiple regression that fits into the general linear hypothesis model of full rank. An alternative characterization of the form of the biased estimator has been presented in this note, and an “existence theorem” proven indicating that there exists a k such that the biased estimation based on the proposed characterization would still lead to increased accuracy.     

Peak capacity optimization of peptide separations in reversed-phase gradient elution chromatography: fixed column format

The optimization of peak capacity in gradient elution RPLC is essential for the separation of multicomponent samples such as those encountered in proteomic research. In this work, we study the effect of gradient time (tG), flow rate (F), temperature (T), and final eluent strength (phi(final)) on the peak capacity of separations of peptides that are representative of the range in peptides found in a tryptic digest. We find that there are very strong interactions between the individual variables (e.g., flow rate and gradient time) which make the optimization quite complicated. On a given column, one should first set the gradient time to the longest tolerable and then set the temperature to the highest achievable with the instrument. Next, the flow rate should be optimized using a reasonable but arbitrary value of phi(final). Last, the final eluent strength should be adjusted so that the last solute elutes as close as possible to the gradient time. We also develop an easily implemented, highly efficient, and effective Monte Carlo search strategy to simultaneously optimize all the variables. We find that gradient steepness is an important parameter that influences peak capacity and an optimum range of gradient steepness exists in which the peak capacity is maximized.     

Analysis of four-way two-dimensional liquid chromatography-diode array data: application to metabolomics

Two-dimensional liquid chromatography (2D-LC) is rapidly gaining popularity for the analysis of very complex mixtures, including proteomic and metabolomic samples. It provides an effective strategy for separating such samples, because the resolving power of 2D-LC is far superior to that of traditional single-dimension separations. The present work focuses on the development of data analysis methods for the extremely large data sets, on the order of 10 million data points, generated by 2D-LC with diode-array detection (DAD). Specifically, we have applied and adapted chemometric methods to the analysis of maize seedling digests, focusing on compounds related to the biosynthetic pathways of indole-3-acetic acid, the primary growth regulator in plants. The chemometric techniques of window target testing factor analysis (WTTFA), along with parallel factor analysis - alternating least squares (PARAFAC-ALS) were used to analyze 2D-LC-DAD chromatograms of a sample composed of 26 indolic standards, 2 extracts of mutant orange pericarp maize seedlings, 2 extracts of wild-type maize seedlings, and a blank sample. The indolic compounds studied belonged to six spectrally unique groups, and WTTFA was able to specifically identify the presence or absence of any of the 26 indolic standards in the mutant and wild-type samples. A PARAFAC-ALS algorithm and an ALS algorithm with flexible constraints were successfully applied to resolve the spectrally rank deficient data and to demonstrate the quantitative potential of multivariate curve resolution methods. Using this procedure, 95 total peaks were resolved in the data set analyzed. Of those 95 peaks, 45 were found in both the mutant and wild-type maize samples, 16 peaks were unique to the mutant maize samples, 13 peaks were unique to the wild-type maize samples, and 15 peaks were unique to the standard chromatograms. Of the 26 standards included in the data set, several indole acetic acid conjugates were identified and quantified in the maize samples at levels of approximately 0.3-2 microg/g plant material.