Biomedical subjects
M Kohn
Publications and source records attributed to M Kohn.
Gender differences in age effect on brain atrophy measured by magnetic resonance imaging.
A prospective sample of 69 healthy adults, age range 18-80 years, was studied with magnetic resonance imaging scans (T2 weighted, 5 mm thick) of the entire cranium. Volumes were obtained by a segmentation algorithm that uses proton density and T2 pixel values to correct field inhomogeneities ("shading"). Average (+/- SD) brain volume, excluding cerebellum, was 1090.91 ml (+/- 114.30; range, 822.19-1363.66), and cerebrospinal fluid (CSF) volume was 127.91 ml (+/- 57.62; range, 34.00-297.02). Brain volume was higher (by 5 ml) in the right hemisphere (P less than 0.0001). Men (n = 34) had 91 ml higher brain and 20 ml higher CSF volume than women (n = 35). Age was negatively correlated with brain volume [r(67) = -0.32, P less than 0.01] and positively correlated with CSF volume (r = 0.74, P less than 0.0001). The slope of the regression line with age for CSF was steeper for men than women (P = 0.03). This difference in slopes was significant for sulcal (P less than 0.0001), but not ventricular, CSF. The greatest amount of atrophy in elderly men was in the left hemisphere, whereas in women age effects were symmetric. The findings may point to neuroanatomic substrates of hemispheric specialization and gender differences in age-related changes in brain function. They suggest that women are less vulnerable to age-related changes in mental abilities, whereas men are particularly susceptible to aging effects on left hemispheric functions.
Magnetic resonance imaging in schizophrenia. I. Volumetric analysis of brain and cerebrospinal fluid.
The study reports magnetic resonance imaging data for 42 patients with schizophrenia and 43 normal controls. Volumetric measures were obtained with a validated computerized algorithm for segmentation of cranial volume into brain tissue and central and peripheral cerebrospinal fluid (CSF), with high inter-operator reliability. Patients did not differ significantly in whole-brain volume, but had higher whole-brain CSF volume and higher ratios of ventricular and sulcal CSF to cranial volume. Covarying age and education did not affect the differences. However, there was considerable overlap both in CSF volumes and in volume-cranium ratios, and most patients were within the normal range. This suggests that anatomic changes reflected in CSF can provide a limited substrate for schizophrenia and may apply only to subpopulations. Although there was no gender x diagnosis interaction, the results for sulcal CSF were significant only for men, whereas for women, the ventricular ratios were marginally higher in patients.
Resistance levels of nine mosquito species to 4% DDT in Phnom Penh, Kampuchea.
According to the standard WHO method criteria, the mosquitoes Anopheles campestris and Culex vishnui were found to be susceptible to DDT in the territory of Phnom Penh. An. vagus and An. sinensis were approximately at the limit of susceptibility and the remaining five species (Aedes vexans, Cx. tritaeniorhynchus, Cx. fuscocephala, Cx. gelidus, Cx. bitaeniorhynchus) were found to be more or less resistant. Except for An. vagus, the males of all species were more susceptible than the females.
Susceptibility of adult Aedes aegypti (L.) and Culex quinquefasciatus Say (Diptera; Culicidae) to DDT in Kampuchea.
The susceptibility to 4% DDT was tested in adult Aedes aegypti and Culex quinquefasciatus mosquitoes collected in houses in Phnom Penh (Kampuchea). It was found that in spite of the fact that insecticide treatment had not been performed for many years, the populations of both species as a whole remained resistant. However, there were some differences in the susceptibility between males and females and between engorged and hungry females. Possible causes of these differences are discussed in the present paper.
Occurrence of Aedes aegypti (L.) and Culex quinquefasciatus Say (Diptera, Culicidae) in houses of different constructions in Phnom Penh, Kampuchea.
The relation between the number of mosquito specimens of the most abundant species Aedes aegypti (L.) and Culex quinquefasciatus Say and the construction of houses which they inhabited was studied. The effect of the building materials and of the height at which the floor was situated above the ground were assessed in five and four localities, respectively. It was found that in the localities having the character of a town the mosquitoes were most abundant in houses constructed from corrugated plate and in those the floor of which was situated 2-3.5 m above the ground. In the locality of a village character, the mosquitoes were most numerous in brick houses with the floors at the ground level.
Phase I trial with peptichemio.
Thirty-two patients with tumor progression, even after conventional cytostatic drug treatment, were treated with peptichemio, with increasing doses for groups of 4 patients. The maximum tolerated dose (with minimum hematological toxicity and without any other evident toxicity) with repeated administrations, was 1.2 mg/kg twice weekly. The recommended doses for phase II trials are, as shown by the detailed analysis of the results, 0.9 mg/kg, twice weekly and administered alone, and 1.3 mg/kg, once weekly combined with other cytostatic drugs, in 500 ml of infusion fluid, with 25 mg of heparin and 25 mg of hydrocortisone to minimize the freqent risk of local phlebosclerosis.
Social-ecological assessment of environments: toward a two-factor model.
A study was conducted to test the usefulness of the two-factor model in assessing social environments. Subjects were residents and staff at a residential treatment center for emotionally disturbed and/or delinquent boys and girls. Rating instruments consisted of (a) two parallel versions of Moos' Community-Oriented Programs Enivronment Scale (COPES), each worded so as to be appropriate to the setting being measured, and (b) global ratings of satisfaction with the environment. Principal component factor analyses, carried out separately on the youths' COPES-School and the youths' COPES-Cottage, yielded two orthogonal but similar factors in each environment. In a comparison with Moos' three-dimensional formulation of the social milieu, the two factors strongly resembled two of Moos' dimensions but were more independent, had greater validity, and discriminated between the two environments at a higher level of significance. The instruments derived from the factor analyses provide a simple procedure for assessing a variety of treatment programs and populations.
An adolescent symptom checklist for juvenile deliquents.
A rating instrument was developed to assess the personality functioning of problem adolescents who have a brief history of official delinquency. Subjects were 186 residents at a short-term diagnostic detention facility. The instrument that emerged from a factor analysis was tested for reliability, validity, and cross-situational generality. Two major orthogonal factors emerged, Apathy-Withdrawal (I) and Anger-Defiance (II). Each factor was found to be congruent with the corresponding dimension on behavior rating instruments that had previously yielded two orthogonal factors and that had been shown to be relevant to a large number of psychological and educational issues. Significant correlations between the factors and a series of global ratings measuring behavior and measures indicative of the frequency and seriousness of official delinquency provided further evidence of construct and discriminant validity as well as evidence of cross-setting consistency of personality functioning.
Characteristics of families coming to the family court on PINS petitions.
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Averaged evoked potentials and frequency modulation.
Frequency modulated (FM) auditory stimuli result in average vertex potentials similar to the usual auditory average evoked potential (AEP). For stepwise increase or decrease in tone frequency the AEPs are similar. For FM stimuli modulated by pulses of different durations 'on' responses are evoked by the transition of the stimulus from the longer duration to the shorter duration frequency tone while 'off' responses result when the frequency transition is from the shorter to the longer duration tone. Ramp modulation of the stimulus frequency results in average evoked responses; the amplitude of these responses is proportional to the slope of the ramp as well as the frequency of the tone that precedes the ramp. Thus, if the tone preceding the ramp is also a ramp but of smaller slope the AEP is attenuated and with sufficiently large slope the AEP can be completely extinguished. No AEPs were obtained at the offset of ramp modulated stimuli. The standard deviation (S.D.) of the reaction time (RT) distributions to stimulus onset indicate that the AEP amplitude is inversely proportional to the S.D. values. Thus, the attenuation phenomena appeared to be related to the uncertainty of the subject as to the exact time the stimulus occurred, both of which seem to be the result of sensory difficulty to the type of stimuli used. AEPs to negative ramps were smaller than AEPs to positive ramps; this may be on account of the psychological inequality between the stimuli.
Cross-situational consistency among problem adolescents: an application of the two-factor model.
A study was conducted to measure cross-situational consistency of the orthogonal dimensions of the two-factor model of social-emotional functioning. According to this model, large proportions of variance in social-emotional functioning can be accounted for by two orthogonal, highly replicable dimensions. The setting was Hawthorne-Cedar Knolls, a long-term institution for emotionally disturbed and delinquent youths; the subjects were 206 residents of varied ethnic and socioeconomic backgrounds. Cross-situational correlations between school and cottage settings were found to be .52 for Factor II (Cooperation-Compliance versus Anger-Defiance) and .42 for Factor I (Interest-Participation versus Apathy-Withdrawal). The results confirm the consistency and discriminant validity hypotheses--specifically, correlations between the corresponding factors of different instruments measuring behavior in different settings were large, whereas correlations between noncorresponding factors were very low. The value of using broad, higher order factors in personality research on the trait versus situation issue is discussed.
The Kohn Social Competence Scale and Kohn Symptom Checklist for the preschool child: a follow-up report.
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A nonparametric statistical evaluation of changes in evoked potentials to different stimuli.
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Emotional impairment and achievement deficit in disadvantaged children--fact or myth?
This study examined the relationship between demographic and preschool social-emotional variables, on the one hand, and first grade social-emotional and intellectual achievement variables, on the other. Three hundred twenty-three children from New York City public day care centers were followed up 12 and 18 months later in elementary school. Emotional impairment in first grade was found to be a function of social class, race, and preschool emotional impairment. Two major dimensions of social-emotional functioning showed same-factor stability but not cross-factor correlation over time; one of the dimensions (Apathy-Withdrawal) predicted to first grade underachievement.