Decomposing Area of Residence Differences in Multiple Regression Studies: The Relative Contributions of Independent Variables and Model Coefficients

When rural/urban differences are found in health status or health care use, it is often desirable to identify those factors (such as age, social structure, income, etc.) that influence such differences. To this end, researchers often test rural/urban differences in age, social structure, income, etc., for statistical significance. Also, researchers commonly perform multivariate analyses (such as multiple regressions) to examine rural-urban differences in the influence of various independent variables on the dependent variable of interest. Frequently, researchers discover: (1) statistically significant rural/urban differences in the independent variables (such as age, social structure, income, etc.) and (2) statistically significant rural/urban differences in the effects of these independent variables (i.e., statistically significant rural/urban differences in regression coefficients). The analysis typically stops here, without addressing the relative contributions of (1) and (2) to the rural/urban differences in the dependent variable. This paper argues that the relative contributions of (1) and (2) have important implications for the way policy-makers address rural health problems. This paper presents a method for assessing the relative contributions of differences in the independent variables and differences in regression coefficients to observed differences in the dependent variable, and illustrates the application of the method by analyzing rural/urban differences in the risk of institutionalization.     

An analytical solution for the SSFP signal in MRI.

Among previous analyses of the steady-state free-precession (SSFP) signal in rapid MRI, one treatment resulted in equations that require the evaluation of infinite binomial series. Here, an analytical solution is derived by a transformation into the power series expansion of the derivative of the inverse sine function, which is essentially a root. The treatment is extended to include higher-order signals. The results demonstrate the identity of the vastly different equations for the SSFP signals reported so far. Applications consist of the derivation of closed expressions for the signal in echo-shifted MRI and a corresponding analysis of TrueFISP sequences.     

Inhibition and superactivation of the calcium-stimulated isoforms of adenylyl cyclase

It was shown previously that chronic exposure to opiate agonists increases adenylyl cyclase (AC) activity, a phenomenon termed AC superactivation (or supersensitization). More recently, we showed that acute G_i/o-coupled receptor activation inhibits the activity of several AC isozymes, including Ca²⁺/calmodulin-stimulated AC-I and -VIII, whereas chronic receptor activation induces their superactivation. Here, we report that both acute μ-opioid receptor-induced inhibition and chronic induced superactivation of AC-I and -VIII are pertussis toxin sensitive. In addition, we show that proteins that interfere with the activity of {ie195-2} subunits ({ie195-3} scavengers) strongly attenuate the acute inhibition of AC-I and -VIII and the superactivation of AC-I, and abolish the superactivation of AC-VIII. Based on these results, we suggest that {ie195-4} is involved in the acute inhibition and chronic agonist-induced superactivation of AC types I and VIII.     

Effect of Ethanol and Stress on Plasma Catecholamines and Their Relation to Changes in Emotional State and Performance

The "tension reduction hypothesis" of ethanol was investigated with respect to stress- and ethanol-induced changes of plasma catecholamines and their relations to changes in emotional state and performance. Twenty-two healthy male volunteers were tested under the influence of 0.8 g/kg ethanol and compared to 22 matched controls receiving a placebo drink. Stress was induced by mental arithmetic applied prior to and 45 min after fluid consumption. Plasma epinephrine (E) and norepinephrine (NE) obtained from an indwelling cannula inserted 50 min prior to stress application were determined prior to and after each stress session. Percentage changes were compared within and between groups and correlated with respective changes of emotional states and performance in mental arithmetic. While ethanol decreased performance and stress-related emotional arousal, it did not affect stress-induced changes in plasma catecholamines. Rather, the fluid (ethanol as well as placebo) increased NE levels. Emotional tension reduction was associated with low resting or average levels of E in the placebo group but this relationship was disrupted by ethanol. High NE resting levels and drink induced increases predicted emotional tension reduction with placebo but an increase in stress induced depression with alcohol. "Biochemical tension reduction" (represented by both reduced E and NE stress response) may be predicted from generally lower levels of activation and elation by alcohol but not with the placebo condition. Although performance was positively related to low NE resting levels and stress responses, no influence of alcohol on this relationship was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

The surgical treatment of chronic gastric atony following Roux-Y diversion for alkaline reflux gastritis.

Symptoms of severe nausea, vomiting, abdominal pain, and frequent bezoars, as well as objective gastric retention, can occur following Roux-Y biliary diversion for alkaline reflux gastritis. Medical therapy and prokinetic drugs have proven ineffective. This review evaluates 37 patients who underwent further gastric resection from 1979 to 1987 to improve gastric emptying and resolve symptoms. Fifteen patients underwent perioperative radionuclide solid-food gastric emptying studies. Seventy-three per cent (27 of 37 patients) of the patients who underwent further gastric resection (70% to 95%) had a satisfactory postoperative response. Twenty patients were graded Visick 1 or 2 and 7 Visick-3 patients, although much improved, still had some symptoms of gastroparesis. Twenty-seven per cent (10 of 37 patients) failed to improve and underwent completion total gastrectomy. Overall, 70% of this group had almost complete resolution of their symptoms. Three of 10 patients were considered "failures" due to postprandial pain in 1 and early vasomotor dumping in 2. Of the 10 patients who failed initial revisional surgery, 7 underwent a 70% to 80% subtotal gastric resection (STG) and 3 patients underwent 85% to 95% extensive resection (EXT.G.). Of the 15 patients who underwent perioperative radionuclide evaluation, a mean two-hour gastric retention of 61.4% +/- 4% (SEM) decreased to 25% +/- 4% following further gastric resection. Eight patients were in the STG group and seven patients were in the EXT.G group. Following STG, mean two-hour gastric retention of 58.2% +/- 3.5% decreased to 38% +/- 3% (p less than 0.05). In seven patients who underwent EXT.G, mean two-hour retention of 65% +/- 4% decreased to 10% +/- 2.5% (p less than 0.005). EXT.G resulted in normal gastric emptying and few late failures. In post-Roux-Y patients with symptoms of gastroparesis and documented gastric retention, EXT.G normalizes gastric emptying and restores a better quality of life. Total gastrectomy should be reserved for those patients who are failed by more extensive resection.     

Effect of ethanol on plasma amino acids and related compounds of stressed male rats

Plasma amino acid levels in rats are known to be affected by ethanol or by immobilization stress. This paper investigated the effect of ethanol on plasma amino acid levels of stressed rats. Rats received ethanol (2 g/kg, IP) 15 minutes prior to a 30-min immobilization period. Blood samples were obtained from individual rats before, during and after stress. Ethanol lowered the concentration of most plasma amino acids (AA) or related compounds in stressed rats (e.g., aspartic acid, threonine, serine, glycine, alanine, valine, tyrosine, phenylalanine, tryptophan). Some compounds remained unaffected (e.g., taurine, cystine, ethanolamine and methylhistidines) and one (phosphoethanolamine) increased initially. A comparison of the effects of ethanol on plasma AA and related compounds in resting and stressed rats shows similarities and differences. In general, ethanol tends to change the concentrations of these compounds away from normal levels in nonstressed rats, whereas in stressed rats, ethanol tends to antagonize stress-induced changes. This study shows that ethanol can affect individual AA and related compounds differently in nonstressed and stressed rats and that ethanol reduces stress-induced changes. The latter finding supports the "tension-reduction hypothesis" of ethanol.     

The Stockholm breast cancer screening trial — 5-year results and stage at discovery

In screening programmes it is important to assess a preliminary effectiveness of the screening method as soon as possible in order to forecast survival figures. In March 1981 a controlled single-view mammographic screening trial for breast cancer was started in the south of Stockholm. The population invited for screening mammography consisted of 40,000 women aged 40–64 years, and 20,000 women served as a well-defined control group. The main aim of the trial was to determine whether repeated mammographic screening could reduce the mortality in the study population (SP) compared to the control population (CP).The cumulative number of advanced mammary carcinomas in the screening and the control populations from the first five years of screening have shown a tendency towards more favourable stages in the screened population aged 40–64 years. A breakdown by age suggests an effect in age group 50–59 years, but not yet in age groups 40–49 and 60–64 years.When comparing the rates of stage II+ cancer, an increased number is found in the study group. As the total rate of breast cancer is higher in SP than in CP, there ought to be a concealed group of stage II+ cancers in the CP which makes the comparison biased. A new approach has been designed, where an estimation of the hidden number of stage II+ cancers in CP is added to the clinically detected cases, and in this respect a comparison has shown a decrease in the cumulative number of advanced cancers in the SP in relation to the CP (p<0.05). According to this it could be important to add the estimated number of undetected, hidden cases in the control group in order to utilize the difference in detection rate in the screening- and control group respectively.     

Deletion of Brca2 exon 27 causes hypersensitivity to DNA crosslinks,chromosomal instability,and reduced life span in mice

The Brca2 tumor-suppressor gene contributes to genomic stability, at least in part by a role in homologous recombinational repair. BRCA2 protein is presumed to function in homologous recombination through interactions with RAD51. Both exons 11 and 27 of Brca2 code for domains that interact with RAD51; exon 11 encodes eight BRC motifs, whereas exon 27 encodes a single, distinct interaction domain. Deletion of all RAD51-interacting domains causes embryonic lethality in mice. A less severe phenotype is seen with BRAC2 truncations that preserve some, but not all, of the BRC motifs. These mice can survive beyond weaning, but are runted and infertile, and die very young from cancer. Cells from such mice show hypersensitivity to some genotoxic agents and chromosomal instability. Here, we have analyzed mice and cells with a deletion of only the RAD51-interacting region encoded by exon 27. Mice homozygous for this mutation (called brca2(lex1)) have a shorter life span than that of control littermates, possibly because of early onsets of cancer and sepsis. No other phenotype was observed in these animals; therefore, the brca2(lex1) mutation is less severe than truncations that delete some BRC motifs. However, at the cellular level, the brca2(lex1) mutation causes reduced viability, hypersensitivity to the DNA interstrand crosslinking agent mitomycin C, and gross chromosomal instability, much like more severe truncations. Thus, the extreme carboxy-terminal region encoded by exon 27 is important for BRCA2 function, probably because it is required for a fully functional interaction between BRCA2 and RAD51.     

Is the risk of bipolar disorder in twins equal to the risk in singletons? A nationwide register-based study

BACKGROUND: A previous study demonstrated a higher rate of schizophrenia in dizygotic twins than in the general population, and a higher rate of schizophrenia in siblings of dizygotic twins than in siblings of monozygotic twins and singletons, pointing to a common genetic predisposition for dizygotic twinning and schizophrenia. The aim of the present study was to investigate whether these findings also apply to bipolar disorder. METHODS: Through record linkage between The Danish Twin Register, The Danish Psychiatric Central Register and The Danish Civil Registration System, the rate of bipolar disorder (diagnosed for the first time during admission to hospital) in dizygotic and monozygotic twins was compared with the rate in singletons, and the rate in siblings and parents of twins was compared with the rate in siblings and parents of singletons. RESULTS: The rate of bipolar disorder was the same in dizygotic twins, monozygotic twins and singletons as well as for parents and siblings of dizygotic twins, monozygotic twins and singletons. LIMITATIONS: The study is a register-based study, only including hospitalized patients. CONCLUSION: This study shows that there is an equal rate of bipolar disorder in twins and in singletons. Assuming that DZ twinning is under some genetic influence, a differential relationship between schizophrenia and DZ twinning on one hand and bipolar disorder and DZ twinning on the other hand may suggest differences in the genetic basis of the two diseases. The finding that the rate of bipolar disorder in monozygotic twins is the same as the rate of bipolar disorder in singletons supports studies finding no association between bipolar disorder and obstetric complications.