PubMed Health⌕ Search

Biomedical subjects

J C Simpson

Publications and source records attributed to J C Simpson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Testing for interaction between maternal smoking and TGFA genotype among oral cleft cases born in Maryland 1992-1996.

OBJECTIVE: Infants born in Maryland between June 1992 and June 1996 were used in a case-control study of nonsyndromic oral clefts to test for effects of maternal smoking and a polymorphic genetic marker at the transforming growth factor alpha (TGFA) locus, both of which have been reported to be risk factors for these common birth defects. DESIGN AND SETTING: Cases were infants with an oral cleft ascertained through three comprehensive treatment centers, with additional ascertainment through a registry of birth defects maintained by the Maryland Health Department. Controls were healthy infants. Medical history information on infants and mothers were collected, along with DNA samples. PATIENTS, PARTICIPANTS: Among 286 cases contacted (72% ascertainment), there were 192 nonsyndromic isolated oral clefts (106 M; 86 F) available for this case-control study. MAIN OUTCOME MEASURES: The largest group of 149 Caucasian nonsyndromic cases and 86 controls was used to test for association with maternal smoking and genotype at the Taq1 polymorphism in TGFA. RESULTS: While this modest sample had limited statistical power to detect gene-environment interaction, there was a significant marginal increase in risk of having an oral cleft if the mother smoked (odds ratio = 1.75, 95% CI = 1.01 to 3.02). We could not demonstrate statistical interaction between maternal smoking and TGFA genotype in this study, however, and the observed increase in the C2 allele among cases was not statistically significant. CONCLUSIONS: We could not confirm either the reported association between oral clefts and TGFA genotype or its interaction with maternal smoking. However, these data do show an increased risk if the mother smoked during pregnancy, and this effect was greatest among infants with a bilateral cleft and no close family history of clefts.

Alleles↗
PubMed1996

Free ricin A chain reaches an early compartment of the secretory pathway before it enters the cytosol.

During the intoxication of mammalian cells by ricin, the catalytically active A chain must cross the membrane of an intracellular compartment in order to reach its ribosomal substrates in the cytosol. The actual site of ricin A chain translocation is unclear, and conflicting views hold that it enters the cytosol from endosomes or from an early compartment of the secretory pathway, possibly the lumen of the endoplasmic reticulum. Here we show that treating cells with brefeldin A, or transiently overexpressing mutant GTPases known to inhibit biochemical complexes mediating anterograde and retrograde transport between the endoplasmic reticulum and the Golgi complex, protected cells from intoxication by free ricin A chain. These data indicate that ricin A chain, either free or as part of intact ricin, reaches an early compartment of the secretory pathway before translocation into the cytosol occurs.

Amino Acid Sequence↗
PubMed1996

Mortality among patients with schizophrenia.

Results from a 40-year followup study of psychotic patients are presented to illustrate some of the major findings and unanswered questions about excess mortality in schizophrenia and to suggest analytical approaches that take full account of the potential effects of sample heterogeneity. In this study, hospital-diagnosed schizophrenia patients were at increased mortality risk whether or not they met research criteria for schizophrenia. In addition, mortality outcomes of several major diagnostic groups were similar despite substantial clinical and demographic differences between the groups at baseline. These results suggest that both diagnosis-specific and nondiagnostic factors are needed to account for excess mortality in patients with major psychiatric disorders. The issue of heterogeneity is also crucial for the clinical purposes of predicting and ultimately reducing the mortality risk of psychiatric patients, for example, in delineating profiles of high-risk patients who are not necessarily typical of other patients with the same diagnosis.

Adult↗
PubMed1996

Reconstruction of radionuclide releases from the Hanford Site, 1944-1972.

Historic releases of key radionuclides were estimated as a first step in determining the radiation doses that resulted from Hanford Site operations. The Hanford Site was built in southcentral Washington State during World War II to provide plutonium for the U.S. nuclear weapons program. As part of the Hanford Environmental Dose Reconstruction (HEDR) Project, releases to the Columbia River of 24Na, 32P, 46Sc, 51Cr, 56Mn, 65Zn, 72Ga, 76As, 90Y, 131I, 239Np, and nonvolatile gross beta activity from operation of eight Hanford single-pass production reactors were estimated. Releases of 90Sr, 103Ru, 106Ru, 131I, 144Ce, and 239Pu to the atmosphere from operation of chemical separation facilities were also estimated. These radionuclides and the atmospheric and Columbia River pathways were selected for study because scoping studies showed them to be the largest contributors to dose from Hanford operations. The highest doses resulted from releases to the atmosphere of 131I from chemical separations plants in the pre-1950 period. Prior to 1950, the technology for limiting iodine releases had not been developed. Hence, a very detailed reconstruction of the hourly 131I release history was achieved for 1944-1949 using Monte Carlo methods. Atmospheric releases of the other radionuclides were estimated on a monthly basis for 1944-1972 using deterministic calculations. Monthly releases to the Columbia River for 1944-1971 were based on Monte Carlo methods.

Air Pollutants, Radioactive↗
PubMed1995

Point mutations in the hydrophobic C-terminal region of ricin A chain indicate that Pro250 plays a key role in membrane translocation.

A series of mutations have been made in the carboxyl terminus of ricin A chain, centred on the hydrophobic region between amino acid residues Val245 and Val256. The mutant ricin A chains were expressed to a high level in an Escherichia coli system and the proteins purified to homogeneity. The enzymic activity of each of these A chain molecules was tested on rabbit reticulocyte ribosomes; in all cases, the activities were found to be comparable to wild-type recombinant ricin A chain. Following reassociation of these A chains to ricin B chain, Vero cells were challenged with these holotoxins and the cytotoxicities determined. Mutant ricin A chain with Ile247-->Ala was unable to reassociate and form holotoxin, indicating the importance of this residue in the interaction with ricin B chain. Mutant ricin A chain with Pro250-->Ala readily reassociated with ricin B chain, forming holotoxin with a 170-fold reduction in cytotoxicity to Vero cells. Other mutations in this region also produced A chain proteins which gave marked reductions in holotoxin cytotoxicity. We propose therefore that the C-terminal hydrophobic region of ricin A chain may be involved in membrane interactions prior to the translocation of this subunit into the cytosol, and that Pro250 plays a key role in one or both of these steps.

Amino Acid Sequence↗
PubMed1995

Ricin cytotoxicity is sensitive to recycling between the endoplasmic reticulum and the Golgi complex.

Cytotoxic proteins that kill mammalian cells by catalytically inhibiting protein synthesis must enter the cytosol in order to reach their substrates. With the exception of diphtheria toxin, which enters the cytosol from acidified endosomes, the intracellular site of translocation of other toxins including ricin, Escherichia coli Shiga-like toxin-1, and Pseudomonas exotoxin A is likely to involve early compartments of the secretory pathway. We have used a molecular approach to identify the site and mechanism of toxin delivery to the cytosol by transiently expressing mutant GTPases that inhibit the assembly of biochemical complexes mediating anterograde and retrograde transport in the exocytic and endocytic pathways. The results provide evidence to suggest that receptors actively recycling between the endoplasmic reticulum and terminal Golgi compartments are essential for toxin translocation to the cytosol from the endoplasmic reticulum. The rapid kinetics of intoxication demonstrate a substantial level of bidirectional membrane flow and sorting through the early secretory pathway.

Amino Acid Sequence↗
PubMed1995

Catalytic and cytotoxic activities of recombinant ricin A chain mutants with charged residues added at the carboxyl terminus.

Ricin A chain (RTA) mutants which had been modified by the addition of three lysine residues, three lysines and an alanine, or six histidine residues at the carboxyl terminus were expressed in Escherichia coli. The recombinant proteins were purified to homogeneity by ion-exchange chromatography on CM-Sepharose CL-6B. The 28S ribosomal RNA N-glycosidase activities of the three RTA mutants were indistinguishable from each other and from the activity of wild-type recombinant RTA. The RTA mutants were not impaired, compared with wild-type RTA, in their ability to reassociate with ricin B chain to form ricin holotoxin. Holotoxins containing mutant RTAs were as readily dissociated into subunits under reducing conditions as native holotoxin, and the RTA mutants were indistinguishable from wild-type RTA in the extent of their interaction with biological membranes. Ricin holotoxins containing the RTA mutants were, however, less cytotoxic to Vero cells than ricin containing wild-type RTA. At equivalent concentrations, a time course assay showed that holotoxin containing the mutant RTAs took longer to kill target cells than that containing wild-type recombinant RTA, suggesting that the mutant forms of RTA are less efficiently processed or translocated across an intracellular membrane than is wild-type RTA.

Amino Acids↗
PubMed1992

Mathematical models of complex dose-response relationships: implications for experimental design in psychopharmacologic research.

We develop a mathematical model to account for the complex relationship between drug dose and clinical response in psychopharmacologic research. The model specifies relationships among drug dose, drug bioavailability, pharmacokinetic factors, course moderators, clinical response and the heterogeneity of the disorder, and allows for the derivation of results that have implications for experimental design in psychopharmacologic research. These results form the basis for computer simulations which indicate that random assignment to two fixed doses is more powerful and less sensitive to heterogeneity than assignment to clinically determined doses. Fixed dose designs, however, tend to overestimate the magnitude of drug bioavailability-clinical response relationships. Clinically determined dose designs are useful in some experimental situations; their effectiveness is enhanced by systematically reducing the clinically determined dose. Larger dose reductions improve the ability to detect bioavailability-clinical response relationships.

Antipsychotic Agents↗
PubMed1990

The role of gender in identifying subtypes of schizophrenia: a latent class analytic approach.

Past literature suggests that schizophrenic men and women may be at different risks for developing different subtypes of schizophrenia. This hypothesis was tested using data from the well-known retrospective cohort family studies, the Iowa 500 and the Iowa non-500. The sample consisted of 171 male and 161 female DSM-III schizophrenic patients and 713 of their first-degree relatives. First, bivariate tests for gender differences were conducted regarding family morbidity, age of onset, premorbid history, season of birth, and expression of deficit and affective symptoms. Restricted maximum likelihood latent class analysis was then used to test whether there was a subgroup of schizophrenic men who were more likely to have a low familial risk for schizophrenia or schizophrenia spectrum disorders, deficit symptoms, poor premorbid history, and birth in the winter months, suggesting possible early environmental insults, compared to schizophrenic women. Results showed that although men were more likely to meet these criteria, women also met them, thus suggesting gender differences in the prevalence of the subtype. Schizophrenic women were more likely to express a form of the illness characterized by dysphoria, persecutory delusions, and a higher family morbidity risk for schizophrenia than schizophrenic men. Results for spectrum disorders among relatives were equivocal with regard to gender.

Adult↗
PubMed1988

Outcome studies of schizoaffective disorders.

Outcome studies of schizoaffective disorder have taught us much about the long-term consequences of the syndrome, and they have provided some indication of the potential usefulness of maintaining "schizoaffective disorder" as a diagnostic category separate from schizophrenia and major affective disorder. In a review of outcome studies that compared schizoaffective patients to schizophrenic or affective patients, we found consistent results despite wide variations in diagnostic criteria, length of followup, and demographic characteristics. Global measures of outcome show that schizophrenic patients are more impaired than schizoaffective patients, who in turn are more impaired than affective patients. However, studies of specific outcome domains such as symptomatology, social functioning, and occupational functioning indicate that schizoaffective disorder is heterogeneous and that subtyping by polarity (e.g., schizoaffective-manic vs. schizoaffective-depressed) accounts for some of this variance. The consistency of these findings in the face of methodological variability suggests that it would be premature to classify schizoaffective patients with schizophrenia or affective disorder, but also that strict diagnostic criteria for schizoaffective disorder are at best preliminary and need to be thoroughly validated.

Bipolar Disorder↗
PubMed1986

Cardiac surgery in Jehovah's witnesses. A review of 36 cases.

Between January 1971 and January 1985, 31 Jehovah's witnesses underwent 24 bypass and 12 non-bypass cardiothoracic operations at the National Heart Hospital. Fifty-eight% of the group were under 16 years of age. There was one death in the non-bypass group unrelated to blood loss. Six deaths occurred in the bypass group. In one of these, blood loss contributed to the cause of death and in two patients, blood loss was directly related to the cause of death. The anaesthetic management of Jehovah's witnesses undergoing cardiac surgery is discussed.

Adolescent↗
PubMed1986

Ten-year follow-up of drug abusers with acute or chronic psychosis.

To assess whether long-term outcome of former drug abuse patients who had psychotic symptoms was related to duration of psychosis before hospitalization, the authors rated the psychiatric, occupational, and residential outcome of 101 former drug abuse patients based on interviews conducted ten years after their admission to a psychiatric hospital. At admission, 45 had had psychotic symptoms for six months or more; 26 had had psychotic symptoms for less than six months; and 30 had not been psychotic. Seventy-one former psychiatric patients who had had a psychotic illness but had not abused drugs were also interviewed and rated. Drug abusers with chronic psychosis had significantly worse psychiatric outcome than the other drug abusers and significantly worse occupational outcome than acutely psychotic drug abusers. The authors conclude that drug abusers with chronic psychotic symptoms are a distinct subgroup of drug abusers who suffer from major psychotic illness.

Acute Disease↗
PubMed1985

Mortality studies in psychiatry. Should they stop or proceed?

Psychiatry as a medical discipline has a special concern for preventing premature deaths in psychiatric patients. Such patients continue to be at excess mortality risk despite changing patterns of causes of death and improvements in the treatment of some diagnostic groups. In this overview of current findings and research trends, we find a continuing need for mortality studies and increased opportunities for integrating these investigations with other longitudinal studies of psychiatric populations.

Follow-Up Studies↗
PubMed1985

Are there sex differences in the long-term outcome of schizophrenia? Comparisons with mania, depression, and surgical controls.

Female schizophrenics have been reported to have a better prognosis than male schizophrenics. However, earlier reports rarely used either operational criteria for schizophrenia or appropriate comparison groups. Using data collected as part of a long-term follow-up and family study, the authors examined outcome by sex of 186 schizophrenics, 212 depressives, 86 manics, and 145 surgical controls. When the authors controlled for differences in the age and sex distributions of the diagnostic groups, sex did not make a significant contribution to the explanation of outcome differences between diagnoses or within diagnoses. Examination of outcomes within diagnoses revealed only a nonsignificant trend for female manics to have a better long-term outcome than male manics.

Adult↗
PubMed1985

Contamination of internal jugular cannulae.

137 internal jugular vein cannulae from 113 patients undergoing open heart surgery were cultured using standard broth culture and a semiquantitative culture technique. 60 of the cannulae were placed using an aseptic technique and 77 using a standard non sterile technique. Significant contamination was found in 18.3% of the cannulae in the aseptic group and 15.6% in the standard group. The contaminating organism was Staphylococcus epidermidis in 87.1% of cases. No advantage in using an aseptic technique of cannula insertion was demonstrated. It was concluded that the major source of contamination was elsewhere.

Antisepsis↗