Self-restraint and self-injury: occurrence and motivational significance.

The occurrence of self-restraint was examined in a sample of 99 adults with severe or profound mental retardation who exhibited self-injury. Results showed that 46% of the sample exhibited self-restraint. A significantly higher occurrence of compulsive behaviors was found for subjects who engaged in self-injury and self-restraint when compared to self-injury subjects without self-restraint. To determine the motivational significance of self-restraint, we assessed the response to brief interruption of this behavior. Subjects who engaged in self-restraint responded more negatively to response interruption than did control subjects. These preliminary findings support the hypothesis that self-injury may be related to a compulsive behavior disorder in some individuals who self-restrain.

Growth differences associated with compulsive and stereotyped behavior disorders in adults with mental retardation.

We have recently observed that compulsive behaviors in mentally retarded patients appear to be quite prevalent, can be reliably assessed, and have a high rate of co-occurrence with stereotyped and self-injurious behaviors in this population. As abnormal growth rate has been observed in obsessive-compulsive disorder (OCD) patients, we examined physical stature in adults with mental retardation who display repetitive movement disorders. Identification of cases with stereotypic movement disorder, and cases with compulsive behaviors was done using a symptom checklist and direct observation. Subjects with repetitive movement disorders were smaller in stature than control subjects, with gender differences observed across repetitive behavior disorders. Specifically, female subjects with compulsive behavior disorder, but not stereotypic movement disorder, were significantly shorter and weighted significantly less than same sex-matched controls. Conversely, male subjects with stereotypic movement disorder, but not compulsive disorder, were significantly shorter and weighed significantly less than same sex controls. These findings may point to a neuroendocrine abnormality associated with repetitive movement disorders.

Compulsions in adults with mental retardation: prevalence, phenomenology, and comorbidity with stereotypy and self-injury.

A variety of conceptual similarities between compulsions seen in individuals with obsessive compulsive disorder and stereotypy and self-injury seen in individuals with mental retardation led us to investigate the prevalence, phenomenology, and comorbidity of compulsions in adults with severe or profound mental retardation. We developed simple assessment screening instruments for stereotypy and self-injury and used Gedye's Compulsive Behavior Checklist and found acceptable levels of reliability, stability, and validity for each instrument. Prevalences were as follows: stereotypy: 60.9%; self-injury: 46.6%; and compulsion: 40%. The occurrence of compulsions was significantly positively associated with the occurrence of stereotypy, self-injury, and stereotypy plus self-injury.

Sources, Fluxes, and Sinks of Nitrogen during Early Reproductive Growth of Maize (Zea mays L.).

A study was designed to (a) identify sources and sinks of N in the maize (Zea mays L.) shoot, by estimating net N fluxes for each of seven parts of the shoot, (b) determine effects of N entering the plant upon fluxes of N absorbed before reproductive growth, and (c) determine the effects of the opaque-2 gene on N fluxes in the maize shoot during early reproductive growth. Plants of a maize hybrid (Pioneer 3369A) and its opaque-2 counterpart (Pioneer L3369) were grown in a greenhouse using nutrient solution/sand culture, with NO(3) (-) as the N source during the vegetative growth phase. Beginning at the time of pollination, the same nutrient regime was continued, except that some plants received no N, and others received 3.75 millimolar (15)N as NO(3) (-)-N.Stalk and leaves were found to be primary N sources for the grain, while shank, husk, and cob acted first as N sinks, then as N sources during reproductive growth. Net fluxes of N for each plant part were estimated by calculating the first derivatives of regression equations used to fit data for N contents of each plant part as functions of time. All parts of the shoot were sinks for exogenous N (absorbed after pollination). Thirty-six days after pollination, the grain contained 60% endogenous N (absorbed before pollination) when 3.75 millimolar NO(3) (-)-N was supplied after pollination. Rates of total N influx to the grain were identical whether or not N was supplied in the nutrient solution during reproductive growth. At 36 days after pollination, less N had accumulated in the grain of the opaque-2 genotype, but otherwise there were no differences in N contents or dry weights of the shoots due to the opaque-2 gene. Absence of N from the rooting medium significantly affected N fluxes throughout the shoot during reproductive growth, but there were no detectable effects of the opaque-2 gene on N fluxes in parts of the plant other than the grain.