Reversion of a Chinese Hamster Cell Auxotrophic Mutant

A mutant cell strain derived from a Chinese hamster line by mutagenesis with ethylmethane sulfonate requires glycine for growth. In the wild type, glycine synthesis is catalyzed by serine hydroxymethyltransferase (EC 2.1.2.1). Cell fractionation by differential centrifugation and isopycnic sucrose gradient analysis reveals that the enzyme activity is found in both the mitochondrial and cytosol fractions. The specific activity in the mitochondrial fraction is about 20 times higher than in the cytosol, and is much more stable to thermal inactivation. The glycine-requiring mutant has lost all of the mitochondrial enzyme activity, while retaining the cytosol activity. The mutant is very stable but can be induced to revert by several chemical mutagens. One glycine-independent revertant induced by ethyl methane sulfonate was studied in detail. Serine hydroxymethyltransferase activity is again present in the mitochondrial fraction, at about [unk] of the wild-type level. However, the revertant mitochondrial enzyme exhibits an altered thermal sensitivity, with a half-life at 45 degrees of 55 min as compared to 180 min in the wild type. The half-life for the cytosol enzyme in all three strains is 7 min. Mixing experiments demonstrate that the heat lability of the revertant enzyme is not due to a dissociable factor in the extract. The data are consistent with the idea that the original mutation occurred in the structural gene for one isozyme of the enzyme and that the revertant has undergone a second mutation in this gene, partially restoring enzyme activity.     

Radiation-induced malignant fibrous histiocytoma of the brachial plexus

Summary Brachial plexopathy is a common and disabling complication in cancer patients most often attributed to metastasis or radiation-induced fibrosis. Occasionally, other rare but potentially treatable causes are found. A 73 year old woman had a left radical mastectomy followed by radiation to the chest wall and axilla 24 years ago. She recently presented with left arm pain, chronic, nonprogressive lymphedema, profound distal arm sensory loss and progressive severe hand weakness. There was moderate atrophy of all intrinsic hand muscles, anesthesia of the hypothenar eminence and 4th and 5th digits, and no adenopathy or palpable mass in the axilla. EMG confirmed a brachial plexopathy. MRI showed loss of tissue planes consistent with radiation fibrosis, but CT showed a discrete mass in the brachial plexus. Open biopsy showed pleomorphic spindle shaped cells with immunoperoxidase stains consistent with malignant fibrous histiocytoma.Radiation-induced malignant fibrous histiocytoma may present with a brachial plexopathy in the absence of a palpable mass and should be considered in the differential diagnosis of brachial plexus lesions in cancer patients. CT scanning through the plexus may be useful when MRI is normal or equivocal.     

Managing community and neighborhood partnerships in a community-based nursing curriculum.

A community-based undergraduate nursing program in a liberal arts college sought to establish partnerships with area neighborhoods to enhance the educational process of the program and the health of the neighborhoods. With the full financial and emotional support of the college administration, two unique positions were developed within the nursing department: community partnership coordinator (CPC) and neighborhood coordinator. The CPC works at the greater community level with involvement in area-wide community health ventures to provide a liaison to the community for the nursing department. The CPC coordinates area-wide student experiences, provides oversight to the community-based participatory research process, and expands scholarly opportunities for students and faculty. In addition, a neighborhood coordinator for each of the three underserved, ethnically diverse partnering neighborhoods provides an ongoing presence in the neighborhood, coordinating and teaching students as they have practicum experiences within the neighborhood. The neighborhood coordinator is also intimately involved in the neighborhood, maintaining professional relationships with neighborhood residents, leaders, agency representatives, and health care professionals. Discussion of how challenges of the roles were managed is included.     

Emotional cognizance & the type a behaviour pattern: Urinary catecholamine excretion and self-reported frequency of emotional signs/symptoms

Thirty-eight, first year osteopathic medical students provided a morning and afternoon urine sample (analyzed for norepinephrine and dopamine) on a school day. Change from morning baseline served as a measure of naturally induced arousal (i.e., ?stress”?) to a routine school day. They were also asked to fill out questionnaires assessing mood state during the morning session and, during the afternoon session, Type A Behavior, the frequency of 61 signs/symptoms of emotional arousal since the morning session and control data. One hundred and twenty-two Emotional Dyscognizance Indices (cross-sample t-scores for the two urinary amine measures minus t-scores for the 61 emotional frequency scores) were calculated. Each was then correlated with the Type A measure and 21 (17.2%) proved positive and statistically significant (p < .05). None were negative and statistically significant. The probability of such a finding is less than .001. Current results are consistent with the hypothesis of a heightened sympathoadrenomedullary arousal threshold for experiencing a given intensity of negative emotion in the Type A person. Such emotional dyscognizance would cause problems for both diagnosis and treatment.     

Sample size and power for case-control studies when exposures are continuous

In estimating the sample size for a case-control study, epidemiologic texts present formulae that require a binary exposure of interest. Frequently, however, important exposures are continuous and dichotomization may result in a 'not exposed' category that has little practical meaning. In addition, if risks vary monotonically with exposure, then dichotomization will obscure risk effects and require a greater number of subjects to detect differences in the exposure distributions among cases and controls. Starting from the usual score statistic to detect differences in exposure, this paper develops sample size formulae for case-control studies with arbitrary exposure distributions; this includes both continuous and dichotomous exposure measurements as special cases. The score statistic is appropriate for general differentiable models for the relative odds, and, in particular, for the two forms commonly used in prospective disease occurrence models: (1) the odds of disease increase linearly with exposure; or (2) the odds increase exponentially with exposure. Under these two models we illustrate calculation of sample sizes for a hypothetical case-control study of lung cancer among non-smokers who are exposed to radon decay products at home.     

Radioimmunoassay of O6-methyldeoxyguanosine in DNA of cells alkylated in vitro and in vivo

The legend to Figure 6 should read: Fig. 6. Removal of O⁶-MedG in Chinese hamster cells. V79 (O)and V79/79 (•) cells were exposed to 2.0 mM MNU in culturemedium for 30 min at 37°C.     

The influence of vitamin C on antipyrine pharmacokinetics in elderly men

The influence of vitamin C on the pharmacokinetics of antipyrine was investigated in eleven elderly men aged 65–74. Antipyrine (15 mg kg^?1) was administered intravenously on three separate occasions over a 7-week period: (a) before dietary vitamin C restriction, (b) after approximately 5 weeks of dietary vitamin C restriction, and (c) after 2 weeks of vitamin C supplementation (500 mg orally twice daily). The mean plasma and leucocyte vitamin C levels (±S.D.) before vitamin C restriction were 1·26 ± 0·31 mg dl^?1 and 26·6 ± 6·7 μg 10^?8 leucocytes, respectively. These values decreased and then increased significantly following vitamin C restriction and supplementation, respectively. The mean plasma half-life of antipyrine was 10·2h and the mean plasma clearance was 2·561h^?1 1·73 m^?2 before vitamin C restriction. No significant changes in the clearance, volume of distribution, or half-life of antipyrine occurred during the study, indicating that short-term alterations in vitamin C intake do not affect the pharmacokinetics of antipyrine in elderly males.     

Hiding Worries from One's Spouse: Associations Between Coping via Protective Buffering and Distress in Male Post-Myocardial Infarction Patients and Their Wives

The relationship between protective buffering, a style of coping in which the individual hides his/her concerns from spouse, and level of distress was studied among post-myocardial infarction (MI) patients and their spouses. Forty-three male married MI survivors and their wives completed measures of psychological distress and protective buffering at 4 weeks and 6 months post-hospital discharge. At both time periods, a greater propensity for protective buffering by the patient was related to higher levels of patient distress. Protective buffering by wife was also associated with higher levels of wife distress. In addition, patient buffering at 4 weeks predicted increased patient distress at 6 months. The results suggest that male MI patients who conceal their worries from their spouses adjust more poorly over time.