Use of seminiferous tubule segments to study stage specificity of unscheduled DNA synthesis in rat spermatogenic cells

DNA repair in spermatogenic cells at various stages of maturity was determined by quantitation of unscheduled DNA synthesis (UDS). Male F-344 rats were exposed (i.p.) to methyl methanesulfonate (MMS, 35 mg/kg); 1 hr later, segments of seminiferous tubules corresponding to spermatogenesis stages II, IV-V, VI, VII, VIII, IX-X, XII, and XIV were isolated with the transillumination pattern of the tubules as a guide. Intact tubule segments were cultured 24 hr in the presence of [3H]thymidine, and UDS was quantitated by autoradiography as net grains/nucleus (NG). In primary spermatocytes from treated rats, NG count increased with increasing maturity from leptotene primary spermatocytes (3.5 NG) up through stage VIII and IX-X pachytene spermatocytes (22 NG), after which NG decreased in stage-XII pachytene and diplotene spermatocytes (to 16 NG and 8 NG, respectively). Round spermatids of steps 2-8 of spermiogenesis all exhibited approximately the same UDS response (8 NG). Elongating spermatids as mature as step 14 underwent UDS after exposure to MMS, but step-15 and later-step spermatids did not. The DNA repair response of pachytene spermatocytes cultured within segments of seminiferous tubule corresponding to stages VIII and IX-X was 4 to 25 times greater, depending on the dose of MMS, than pachytene spermatocytes isolated by enzymatic digestion and cultured in suspension [Bentley and Working, Mutat Res 203:135-142, 1988]. Thus, the use of segments of seminiferous tubule both increased the sensitivity of UDS as an indicator of DNA damage in rat germ cells and enabled the study of UDS in spermatogenic cells at different stages of maturity.     

A histopathologic evaluation of nevocellular nevi in pregnancy

A detailed histopathologic study was performed on 128 nevi removed from 86 pregnant white patients. None of the patients had clinical evidence of the dysplastic nevus syndrome, and none of the excised nevi were clinically suspicious for melanoma. One third of patients reported some change in nevi during pregnancy. Nevi from an age-matched male control population (50 patients) had a spectrum of histologic features essentially identical to the pregnant patients, while nevi from a female control population (51 patients) showed slightly less atypia according to our criteria. The differences found between the nevi from pregnant and control women suggest that a mild degree of histopathologic atypia or "activation" is associated with pregnancy. However, in the population studied, these changes were never of sufficient degree to result in diagnostic confusion.     

Current tuberculosis screening practices.

Health department officials in all 50 states and 14 major cities responded to a survey questionnaire designed to obtain information about current tuberculosis screening practices. Persons being screened fell into the groups designated as high risk by the American Thoracic Society (ATS) and the Centers for Disease Control (CDC). The methods used for screening were generally those advocated by ATS, CDC, and the Food and Drug Administration (FDA), although chest radiographs continue to be overused. Screening in about one-half of the groups is mandated by law or regulation. There appears to be some confusion about the circumstances in which "two-step" tuberculin testing should be used. Data on the productivity and costs of screening activities were very limited. We encourage those responsible for tuberculosis screening programs to evaluate them, discontinue those which are unproductive, and intensify those which are productive.     

Proteoglycan depletion alone is not sufficient to stimulate proteoglycan synthesis in cultured bovine cartilage explants

Articular cartilage comprises a small number of cells embedded within a matrix primarily composed of collagen and proteoglycan (PG). The functional integrity of the tissue is highly dependent on the maintenance of matrix structure, which, in turn, is controlled by the chondrocytes. In normal tissue there is a slow but steady turnover of matrix components such that their levels remain constant. In certain diseased states the equilibrium is upset, resulting in a net loss of matrix components. The object of the present study was to artificially upset the synthetic/loss equilibrium by enzymic depletion and assess the ability of chondrocytes to respond by increasing PG synthesis. Cultured bovine articular cartilage explants were depleted using enzymes as follows; 10 U/ml Streptomyces hyaluronidase (induced a 30% loss of PG), 2000 U/ml testicular hyaluronidase (70% loss of PG) and 100 U/ml collagenase (35% loss of PG) and control (6% loss of PG). Collagenase also induced a 50% loss of collagen. Collagenase treatment induced a 50% stimulation of PG synthesis above control levels. Elevated synthesis levels were maintained for 9 days. Testicular hyaluronidase induced a brief elevation in PG synthesis on day 3 of culture. Streptomyces hyaluronidase treatment did not cause an alteration in the rate of PG synthesis above control levels. Histological examination indicated that collagenase-treated explants formed outgrowths consisting of rounded chondrocytes within a fine fibrous matrix which stained intensely with safranin-O, indicating a high concentration of PG. The production of repair-like outgrowths may explain the elevated PG synthesis rates measured. It appears, therefore, that collagen and matrix organization is more important than PG levels in the control of PG synthesis in articular cartilage explant cultures.     

Comparison of benzodiazepine (BZ) receptor agonists in two rodent activity tests

The effects of four BZ receptor ligands in an operant test were compared with a rotarod test. In the operant test, rats were trained to pull a chain on a schedule that regulates the probability of delivery of food pellets to maintain a steady chain-pulling rate across a 1 h test session. For the rotarod test, mice were trained to remain on a rotarod for 2 min. Diazepam (0.1-3.0 mg/kg, i.p.), FG 8205 (0.1-3.0 mg/kg, i.p.), quazepam (3.0-60.0 mg/kg, i.p.) and zolpidem (0.3-10.0 mg/kg, i.p.) each produced dose-related impairments of performance in both the chain- pulling test and the mouse rotarod test. Furthermore, the impairment in performance induced by FG 8205 (10.0 mg/kg, p.o.) was dose-dependently reversed by the BZ receptor antagonist, flumazenil (1.0-10.0 mg/kg, i.p.), indicating that the chain-pulling deficit was mediated via BZ receptor activation. Diazepam, FG 8205 and quazepam all had comparable potencies in both the rotarod assay and the chain-pulling test. However, zolpidem suppressed the chain-pulling rates at a dose 30-fold lower than that required to induce a significant deficit in the rotarod performance. As zolpidem is a preferentially sedative compound, this pattern of results is consistent with the hypothesis that the chain-pulling test is sensitive to sedation induced by BZ receptor agonists.     

Evaluation of possible battlefield tourniquet systems for the far-forward setting

A significant number of casualties in previous conflicts died from peripheral vascular wounds. A well-designed tourniquet could possibly have prevented these deaths. The objective of this study was the identification of such a tourniquet. A survey of Special Operations corpsmen established important characteristics necessary in an ideal tourniquet. Because most available devices do not and patented ideas could not meet these criteria, a number of prototypes were developed. Seven potentially satisfactory tourniquets were evaluated by 15 Navy SEAL corpsmen. The success and timing of placement were recorded, and a follow-up questionnaire was completed. Of the several successful tourniquets, two were preferred. Tourniquets incorporating a windlass technique take longer to place and often fail when placed with only one hand. New, relatively simple tourniquet devices incorporating bladder and ratchet mechanisms can significantly improve tourniquet performance.     

Acceptability of a novel vaginal microbicide during a safety trial among low-risk women

CONTEXT: The increasing recognition that women who are unable or unwilling to discuss or use condoms with their sexual partners need female-controlled methods for preventing sexually transmitted diseases (STDs), including HIV, has led to considerable focus on the development of vaginal microbicides. While many such products are being tested for safety and effectiveness, clinical trials generally overlook another key factor in a product's impact on infection rates-its acceptability to users. METHODS: A Phase I clinical trial of a microbicidal gel included an assessment of the product's acceptability among 27 low-risk participants. Information on acceptability was gathered from structured interviews, participants' daily diaries and unstructured exit interviews. RESULTS: Participants reported only minor side effects of product use, such as itching, burning and difficulty urinating; two women developed candida infections while participating in the study. None of the side effects could be conclusively linked to use of the gel. Some women noted product discharge and messiness as drawbacks of the method, but this experience varied according to how often the women applied the gel. For example, one-third of those who used it once daily said that at least some of the time, it was too "wet or drippy," compared with two-thirds of women who inserted the gel twice a day. However, participants considered these "nuisance factors" that could be outweighed by the potential protective characteristics of the product. The majority reported that they would use the product if it were available and proven efficacious, and if they perceived that they were at risk of STD infection. CONCLUSIONS: Additional testing of this product is urgently needed. Furthermore, as other products approach Phase I testing, acceptability assessments should be a key component of clinical trials.