Collision-induced dissociation of bradykinin ions in the interface region of an ESI-MS.

By applying different electric field strengths to the orifice-skimmer region of an electrospray ionization mass spectrometer, the rate of dissociation can be varied based on the amount of internal energy acquired by an ion through collisions with the curtain gas molecules. Both the Arrhenius equation and Rice-Ramsperger-Kassel (RRK) theory can be used to predict the rate of dissociation of internally excited molecules. A previously determined model for collision-induced dissociation is tested by comparison of predicted and experimentally observed orifice-skimmer potential differences for dissociation of ions. The rate of collision-induced dissociation of bradykinin ions is determined by monitoring the fragments produced in a mass spectrometer. The semi-quantitative model is found to yield effective predictions when accurate Arrhenius and RRK parameters are utilized.

Ion fragmentation in an electrospray ionization mass spectrometer interface with different gases.

Nitrogen, argon, and krypton are used as curtain gases in an electrospray ionization mass spectrometer in an attempt to study the effect of these gases on the extent of ion fragmentation between the orifice and the skimmer of the interface region. A previously published collision model predicts that the degree of ion fragmentation increases with increasing mass of the curtain gas. However, the fragmentation yields are found to be the opposite to that expected. It is believed that the reversed trend with argon and krypton is caused by condensation of the gases within the free jet expansion between the orifice and the skimmer. A condensation parameter can be used to predict the degree of clustering of gases within a free jet expansion. When the condensation parameter is minimized, the predicted trend of fragmentation with mass is observed.

Angelman syndrome.

BACKGROUND: Angelman (happy puppet) syndrome is a neuro-developmental condition characterized by an ataxic gait with puppet-like limb movements, paroxysmal bouts of laughter and severe mental retardation. Although considered a rare condition, over 140 cases have been documented since its designation in 1965. To date, only one study has been published investigating the ocular defects of Angelman syndrome. METHODS: In this paper we report the cognitive, motor, systemic, and oculo-visual findings of a 3 year old child with Angelman syndrome. RESULTS: The oculo-visual findings include choroidal hypopigmentation, iris hypopigmentation, strabismus, and hyperopia. CONCLUSIONS: As in many neuro-developmental conditions, early diagnosis is crucial. The ocular findings of fundal/iris hypopigmentation and strabismus with minimal refractive error in conjunction with the cognitive, behavioral, and motoric characteristics the patient exhibits may be the first clues for the diagnosis of Angelman Syndrome in a developmentally delayed child. The initiation of individualized optometric diagnosis and treatment is important for all children with developmental disabilities. The eye care professional should work in concert with speech, occupational, and physical therapists, neurologists, and special educators in the multi-disciplinary treatment and habilitation of all children with disabilities including those with Angelman Syndrome.

The Pittsburgh Insulin Dependent Diabetes Mellitus Registry: the relationship of insulin dependent diabetes mellitus incidence to social class.

The incidence of insulin dependent diabetes mellitus, as determined from the Pittsburgh Insulin Dependent Diabetes Mellitus Registry, was examined in relationship to social class. The registry consists of all Allegheny County, Pennsylvania, cases of insulin dependent diabetes diagnosed under age 20 years in 1965-1976. Analyses of the registry data revealed little relationship between incidence, age at onset and social class. The lack of a strong relationship to social class indicates that the epidemiology of insulin dependent diabetes is not similar to those of polio or Hodgkin's disease, in which social class is strongly related to incidence and age at onset.

The Pittsburgh insulin-dependent diabetes mellitus (IDDM) registry. The incidence of insulin-dependent diabetes mellitus in Allegheny County, Pennsylvania (1965-1976).

An insulin-dependent Diabetes Mellitus Registry has been developed in Allegheny County, Pennsylvania, through hospital record review and surveillance of pediatric practices. The yearly incidence ranged from 10/100,000 for nonwhite males to 16/100,000 for white males. There were no temporal trends in incidence for 1965-1976 nor major sex differences. Nonwhites had a slightly lower incidence, primarily in the younger age groups.