Modeling the number and size of hepatic focal lesions following exposure to 2,3,7,8-TCDD

Data on the size and number of placental glutathione S-transferase-positive (PGST+) foci were collected from a two-stage hepatocarcinogenesis model in female Sprague-Dawley rats. the study consisted of multiple 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-exposed dose groups including both diethylnitrosomine (DEN)-initiated and uninitiated animals. Groups were observed after 15 or 31 weeks of TCDD exposure. The parameters in the first half of a two-stage mathematical model of carcinogenesis were estimated from these data. If the model is valid, the results suggest that TCDD stimulates the production of PGST+ foci and promotes the growth of PGST+ foci. This finding suggests a complicated mechanism for TCDD-induced production of Hepatic foci that we refer to as activation, labeling TCDD as an activator. The analysis also indicates that there is an interaction between DEN and TCDD which results in dose-related formation of initiated cells throughout the study period. Best-fitting curves (using maximum likelihood methods) for TCDD-induced activation and promotion reached saturation levels at low doses of TCDD. In summary, the model fit the data well, but leads to an interpretation of the data which either questions the validity of the model or implies that our understanding of the effects of TCDD and DEN is incomplete.

Therapy of brown spider envenomation: a controlled trial of hyperbaric oxygen, dapsone, and cyproheptadine

STUDY OBJECTIVE

To determine whether hyperbaric oxygen (HBO), dapsone, or cyproheptadine decreases the severity of skin lesions resulting from experimental Loxosceles envenomation.

DESIGN

Randomized, blinded, controlled study.

SETTING

Animal care facility.

INTERVENTIONS

We used New Zealand white rabbits. All groups received 20 micrograms of pooled L deserta venom intradermally. Our control group received 4 ml of a 5% ethanol solution by oral gavage every 12 hours for 4 days. The HBO group received hyperbaric oxygen at 2.5 ATA for 65 minutes every 12 hours for 2 days, plus 5% ethanol solution for 4 days. The dapsone group received dapsone 1.1 mg/kg in 5% ethanol by gavage every 12 hours for 4 days. The cyproheptadine group received cyproheptadine .125 mg/kg in 5% ethanol by gavage every 12 hours for 4 days.

RESULTS

Total lesion size and ulcer size were followed for 10 days. The lesions were then excised, examined microscopically, and ranked by the severity of the histopathology. The groups did not differ significantly with respect to lesion size, ulcer size, or histopathologic ranking.

CONCLUSION

Given the negative result in this study with adequate power to detect meaningful treatment benefits, we cannot recommend hyperbaric oxygen, dapsone, or cyproheptadine in the treatment of Loxosceles envenomation.

Conservation genetics of the European brown bear--a study using excremental PCR of nuclear and mitochondrial sequences

In the Brenta area of northern Italy, a brown bear Ursus arctos population is rapidly going extinct. Restocking of the population is planned. In order to study the genetics of this highly vulnerable population with a minimum of stress to the animals we have developed a PCR-based method that allows the study of mitochondrial and nuclear gene sequences from droppings collected in the field. This method is generally applicable to animals in the wild. Using excremental as well as hair samples, we show that the Brenta population is monomorphic for one mitochondrial lineage and that female as well as male bears exist in the area. In addition, 70 samples from other parts of Europe were studied. As others have previously reported, the mitochondrial gene pool of European bears is divided into two major clades, one with a western and the other with an eastern distribution. Whereas populations generally belong to either one or the other mitochondrial clade, the Romanian population contains both clades. The bears in the Brenta belong to the western clade. The implications for the management of brown bears in the Brenta and elsewhere in Europe are discussed.

Magnetic resonance imaging in schizophrenia: relationship with clinical measures

Relationships were examined between clinical features of schizophrenia and cerebrospinal fluid (CSF) volume in brain obtained by magnetic resonance imaging (MRI) in a sample of 59 patients. The volumes of the cerebral hemispheres and CSF were measured with a computer program designed to separate reliably neural tissue from CSF. The CSF to cranial volume ratios were related to history, symptom profile and outcome functioning. Earlier age of onset was associated with higher sulcal CSF ratio, r = -0.40. The anatomic measures were unrelated to symptom severity. However, patient subtypes differed in the laterality of measures. Higher left hemispheric ratios were seen in patients with severe negative symptoms, and left predominance of ventricular relative to sulcal ratios was associated with the presence of hallucinations and delusions. The results suggest that while higher CSF is related to earlier age of onset, the clinical symptoms are more related to its lateralization. This is consistent with the hypothesis that schizophrenia is a lateralized brain disease.

The depiction of medical education in medical school catalogs

BACKGROUND

Medical educators bear responsibility for the informational materials that their institutions use to communicate with potential applicants. These documents, because they are often the first official correspondence that prospective students receive, may be influential in shaping students' expectations.

METHOD

In March 1990 all North American medical schools that awarded MD or DO degrees were requested to send their catalogs and courses of study to the authors. In response came 175 documents, with nearly all the schools represented at least once. The photographs and other visual images in these documents were then analyzed from the perspective of a hypothetical applicant who perused what his or her initial request for information had produced.

RESULTS

Nearly 3,400 images were analyzed and categorized according to content and stylistic approach. Two basic stylistic approaches were found: stylized and documentary. Few documents used exclusively one or the other approach, as the approaches represent poles along a continuum. The stylized approach portrays medical education as a product to be sold, whereas the documentary approach candidly tells the story of medical education.

CONCLUSION

The authors conclude that the documentary approach is a more morally responsible way for schools to communicate with individuals who are in the beginning stages of building their mental images of medical education and medical care.

Ligand/receptor binding for 2,3,7,8-TCDD: implications for risk assessment

There is renewed controversy regarding safe exposure levels for dioxin. At the heart of this controversy is the hypothesis that toxic effects of dioxin are receptor-mediated and therefore a "threshold" should exist below which no toxic effects can occur. Our research focuses on the ability of dioxin to alter protein levels in rodent livers. Established effects of exposure to dioxin are the induction of cytochrome P450-1A1 and P450-1A2 and a reduction in the maximal binding of the epidermal growth factor receptor in rat livers. An initiation-promotion protocol was used to study the effects of dioxin in female Sprague-Dawley rats. Animals were administered a single initiating dose of diethylnitrosamine followed by 16 biweekly gavage doses of 2,3,7,8-TCDD. Steady-state pharmacodynamic models were fit to these data assuming a combination of Hill kinetics and Michaelis-Menten kinetics. Two classes of models were developed which postulate two different mechanisms for the constitutive expression and TCDD-induced alterations in the levels of these proteins. The results are consistent with models which follow proportionate response in the low-dose region (no threshold) and with models which allow for a low-dose threshold. In all cases studied, the best fitting model exhibited no "threshold" for the effects of TCDD on the modulation of these proteins. The finding is consistent with the knowledge that for some receptor-mediated responses, there is a proportional relationship between receptor occupancy and biological response, even at low ligand concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Life prolongation: views of elderly outpatients and health care professionals

A peculiar dynamic in communication exists between those who are most likely to be involved in life-prolongation decisions. We found that both the elderly and health care professionals talk about life-prolongation, but not with one another; that they consider some of the same factors as they think about the life-prolongation decision; and that most of them believe physicians should be responsible for initiating discussion. However, the physician or health care professional who wishes to avoid crisis situations also is reluctant to broach the issue for fear of unnecessarily alarming or compromising the defense mechanisms of the patient. The patient remains patient, waiting--with fears of dependency, memories of previous life-threatening experiences, and deep sensitivity for suffering--for the physician to initiate the discussion. Is a mediator such as a family member necessary in these situations? Is the hospital environment not conductive to discussion of less than heroic efforts?

[Induction of objective responses by an anticancer chemotherapy based on the prolonged combination of bleomycin and cisplatin. 1062 cases]

A cis-platin + bleomycin combination, sometimes associated with a third cytostatic drug, was administered for prolonged periods to 1062 cancer patients previously subjected to a wide variety of treatments. The objective response rate was about 70% in localized squamous cell and anaplastic bronchial carcinoma and 40% in bronchial adenocarcinoma and metastatic squamous cell carcinoma. Cancers of the head and neck responded in 70% of the cases before irradiation and in 30% after irradiation. Other epidermoid tumours responded objectively in the proportion of 45%, as did 58% of metastatic and refractory breast cancers. These results were not clearly improved by any of the other cytostatic drugs used concomitantly, and the combination alone was less toxic. The high response rate obtained is attributed to a synergistic effect of cis-platin and bleomycin administered for prolonged periods.

Screening for vesicoureteral reflux in children using real-time sonography

One hundred and ten children, ages 6 days to 14 years, were investigated for vesicoureteral reflux (VUR) using ultrasound before voiding cystourethrography (VCU). Sonographically a VUR was assumed if a retrovesical dilated ureter and/or an increase of the separation of the central renal echo complex (CRC) could be detected. By means of sonography VUR grades III and IV were seen in 100%, grade II in 84% of all cases. There was a false positive rate of 10%. Sonographic reflux study is a sensitive and specific screening and follow-up procedure for VUR.

Average evoked potentials and amplitude modulation

Average auditory evoked potentials (AEPs) to amplitude modulated (AM) linear voltage ramps within a limited intensity range were investigated in a group of 4 subjects. Increasing linear voltage ramps evoked the familiar vertex potential; the average AEP to decreasing ramps was difficult to measure because of its small amplitude. The amplitude of the average AEP to increasing ramps depended on the tone that preceded it. The average amplitude was largest when the tone preceding the onset of the ramp was constant and decreased in amplitude when the slope of the preceding tone deviated from zero either in the positive or negative direction with the positive slope having the more marked attenuating effect. The standard deviation (S.D.) of the distributions of reaction times to stimulus onset correlated negatively with the average AEP amplitude. The attenuation of the averaged AEP appeared to be related to the uncertainty of the subjects as to when the various types of stimuli occurred. The above findings on AM ramp stimuli closely parrellel our previously reported findings on frequency modulated ramp stimuli.

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.

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 frequent risk of local phlebosclerosis.

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.

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.