Antitumor activity of L-canavanine against L1210 murine leukemia.

We have made a preliminary assessment of the antitumor activity of the arginine analog, L-canavanine, in leukemic mice. This analog is known to substitute for arginine in protein biosynthesis in many prokaryotic and eukaryotic systems. Previous studies with cells grown in vitro indicated that canavanine caused a marked inhibition of DNA synthesis and viability. The system used in the present study was C57BL/6 x DBA/2 F mice bearing L1210 leukemic cells. Following an i.v. injection of 10 mg canavanine, the t1/2 beta of canavanine in the serum was estimated at 16 min. This finding suggested that frequent injections of high doses of canavanine would be required for an effect on tumor cell proliferation. DNA synthesis by the L1210 cells, assayed by [3H]thymidine incorporation, fell to 9% of the control value after 12 hourly i.p. injections of canavanine (20 mg each). A constant s.c. infusion of 20 mg/hr for 24 hr caused an 86% inhibition of DNA synthesis. The antitumor activity of canavanine was tested against L1210, using a 24-hr infusion schedule with treatment starting 24 hr after i.p. inoculation of 10(5) cells. An optimal dose of 18 g/kg body weight produced a median increased lifespan of 44% (p less than 0.005). These results suggest that L-canavanine may be useful as an antitumor agent.

An advanced solid support for immunoassays and other affinity applications.

A 6-mm diameter glass bead that has a hydrophilic coating containing epoxy groups has been developed for immunoassays and other affinity applications. These QuantAffinity beads covalently bind protein in the range of 200-400 ng per bead. Derivatization with protein in the presence of high concentrations of potassium phosphate (pH 7.0-8.0) generally gives complete coupling in 16 hours. No preactivation of the support or the protein is necessary. Low nonspecific binding and high retention of bound protein activity are inherent in the system due to the special surface chemistry. Several enzymatic and radioactive immunoassays as well as a biotin-avidin-based assay are described. A use of QuantAffinity beads in small-scale purification is also presented.

Marriage protection and marriage selection--prospective evidence for reciprocal effects of marital status and health.

Married adults are generally healthier than unmarried adults. It has been hypothesized that marriage is associated with good health because marriage has beneficial effects on health (marriage protection effects) and/or because healthier individuals are more likely to marry and to stay married (marriage selection effects). To investigate these hypotheses, this study analyzes prospective panel data for a large national sample of women in the U.S. (the National Longitudinal Surveys of Young Women). The women were aged 24-34 yr at the beginning of two successive five-year follow-up intervals. Analyses of the prospective data indicate that there were significant marriage protection effects, but only among women who were not employed. Specifically, for women who were not employed, married women had better health trends than unmarried women in each follow-up interval. It appears that marriage had beneficial effects on health for women who did not have a job which could provide an alternative source of financial resources and social support. In addition, analyses of the prospective data provide limited evidence for marriage selection effects. Specifically, women who had better health initially were more likely to marry and less likely to experience marital dissolution, but only for women who were not employed full-time and only during the first follow-up interval. Thus, the prospective evidence suggests that, for women who were not employed, both marriage protection and marriage selection effects contributed to the marital status differential in health observed in cross-sectional data. In contrast, neither marriage protection nor marriage selection effects were observed for women who were employed full-time. As would be expected, the cross-sectional data show that marital status differentials in health were large and highly significant for women who were not employed, whereas marital status differentials in health were much smaller and often not significant for employed women. Women who were neither married nor employed had particularly poor health. Additional evidence indicates that the women who were neither married nor employed suffered from multiple interacting disadvantages, including poor health, low incomes, and sociodemographic characteristics which contributed to difficulty in obtaining employment.

Reliability of wound measuring techniques in an outpatient wound center.

Wound measurements determine whether treatment(s) should be continued or changed. A busy wound clinic must rely on many different personnel for wound measurements. The realization that using a variety of measurement techniques could effect medical treatment choices raised concerns. To determine the inter-rater reliability of wound measuring techniques used by clinical staff in an outpatient wound center, three approaches to wound measurement were studied with the intent to standardize clinic procedures in the authors' facilities and to use the method with greatest inter-rater reliability. An exploratory descriptive study was initiated in a busy multidisciplinary wound-healing clinic in a northeastern Ohio 500-bed teaching and community hospital. Participants included 16 wound care professionals who staff an outpatient wound center. Inter-rater reliability measures were compared to three measurement techniques. The intraclass correlation coefficient was used as the statistical measure of inter-observer agreement. After comparing measurements made by the usual method used by an individual, the clockwise method, and the perpendicular method, the perpendicular method showed clear superiority in agreement among clinicians (ICC .962; df = 11,143; P = < 0.001) as compared to the clock-wise method (ICC .682; df = 11,154; P = < 0.05). This study provided a basis for standardizing the approach to wound measurement among physicians and nursing personnel and has important implications for effective medical care, research, and healthcare cost savings.

An update on contraception for adolescents.

Almost one million American adolescents become pregnant each year. Awareness of up-to-date contraceptive methods allows clinicians to appropriately counsel male and female adolescents, preferably prior to the onset of sexual activity. Abstinence, barrier methods, including the female condom and non-latex male condom, and hormonal methods, including oral contraceptive pills, injectables, and subdermal implants, are all suitable for adolescent use. New oral contraceptive pills with lower estrogen content or multiphasic hormone levels may ameliorate side effects, such as headache or breakthrough bleeding. Frank discussion of confidentiality and of the various contraceptive methods and their side effects allows adolescents to choose the best method for them, thus improving the likelihood of adherence.

Replicative activity of histone-deficient SV40 chromatin.

Histone-deficient SV40 chromatin, selectively radiolabeled in the DNA following the addition of cycloheximide to infected monkey cells, was compared with the normal 55S viral chromatin for its ability to serve as a template for a subsequent round of replication. After the removal of cycloheximide, the 26S histone-deficient SV40 chromatin was converted to apparently normal 55S chromatin. During this conversion, the chromatin which sedimented at 26-40S failed to replicate whereas the 44-55S chromatin contained a large fraction (28%) of newly replicated DNA molecules. Thus, the DNA in the 26S histone-deficient 40S chromatin cannot replicate without the prior and/or concommitant addition of protein which increases its sedimentation rate to 41-55S. Nevertheless, when compared with normal 55S viral chromatin, the histone-deficient SV40 chromatin had nearly a 3-fold greater probability of functioning as a template for a subsequent round of replication.

Recently replicated simian virus 40 DNA is a preferential template for transcription and replication.

The template activities for the processes of replication and transcription were compared for recently replicated ("new") and uniformly labeled ("old") simian virus 40 (SV40) DNA in infected monkey cells (line TC7). New SV40 DNA (pulse-labeled for 1 h) served as a template for a second round of replication with a relatively high probability (8% of the DNA replicated per h) for a period of 5 h, after which time its template activity rapidly decreased by severalfold. Old SV40 DNA (labeled for 24 h) functioned as a template for replication with a constant probability (1.8% of the DNA replicated per h) for at least 12 h. The proportion of RNA polymerase with nonreplicated and with recently replicated (bromodeoxyuridine-substituted) viral DNA was determined by an assay that used the Triton-soluble SV40 transcription complex. The proportion of RNA polymerase associated with nonreplicated SV40 DNA decreased very slowly (to 50% in 6 h), strongly suggesting that replicating viral genomes are not required as templates for the initiation of late transcription. This hypothesis was supported by the finding that the RNA synthesized in vitro was associated with covalently closed circular SV40 DNA. Furthermore, after 9 h in bromodeoxyuridine, the recently replicated viral DNA had nearly three times more RNA polymerase per unit of DNA than did the nonreplicated DNA. We thus conclude that recently replicated SV40 DNA is utilized preferentially as a template for transcription and for replication.

The sv40 transcription complex. I. Effect of viral chromatin proteins on endogenous RNA polymerase activity.

SV40 chromatin obtained from infected monkey cells was used to study the effect of the viral chromatin proteins on endogenous RNA polymerase II. Ammonium sulfate activated the rate of transcription by endogenous RNA polymerase in two ways: 1) by direct action on the enzyme; and 2) by causing a reversible conformational change in the viral chromatin. Under optimal reaction conditions, the viral chromatin proteins did not limit the rate of RNA chain elongation, and high molecular weight RNA (1.6 X 10(6) d) was synthesized by the SV40 chromatin.

The sv40 transcription complex. II. Non-dissociation of protein from SV40 chromatin during transcription.

A small fraction of the SV40 chromatin isolated from infected monkey cell cultures by the Triton method contains active RNA polymerase which had initiated transcription in vivo. This viral transcription complex (VTC) was utilized to answer the question of whether proteins dissociate from chromatin during transcription in vitro. 3H-RNA was synthesized by the VTC under conditions such that over half the label was in transcripts which were longer than half the length of the SV40 genome. Virtually all of the 3H-RNA remained associated with the SV40 chromatin, causing an increase in sedimentation rate from 55S to 78S. The density of the VTC-3H-RNA complex indicated that less than 5% of the original protein dissociated from the SV40 DNA which served as a template for transcription. We conclude that SV40 chromatin can be transcribed while the proteins remain associated with the DNA.

Delayed hypersensitivity in patients treated by curative radiotherapy. Its relation to tumor response and short-term survival.

Delayed hypersensitivity, as determined by skin reactivity to 2-4 dinitrochlorobenzene (DNCB), was tested in 112 patients prior to their undergoing curative radiotherapy. Of the strong DNCB reactors, 84% had an excellent radiation tumor response, while only 48% of the negative reactors had an equivalent response. Almost twice as many strong DNCB reactors were alive and free of disease (NED) at 6 months (70% vs. 38% for nonreactors). Similarly, the positive DNCB reactors had a median survival of 18 months, compared to 10 months for the nonreactors.