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Biomedical subjects

D B Brown

Publications and source records attributed to D B Brown.

72 records · Page 4Linked to original sources

Visualization of interphase chromosomes.

Using a modified Giemsa-banding technique we have observed what appear to be chromosomes during interphase in nuclei from Allium cepa root tips and Chinese hamster cells (CHO line). During telophase through G1 chromosomes progressively uncoil and decondense. During S chromosomes are comparatively decondensed, but some segments have structure similar to chromosomes in G1 and G2. During G2 the chromosomes progressively recondense and coil in apparent preparation for prophase. Although specific structural modifications of chromosomes occur in G1, Sand G2 nuclei, chromosomes appear never to decondense to the point that they lose their 3-dimensional integrity, but remain in distinct domains throughout interphase.

Animals↗

The use of an in vitro sperm activation assay to detect chemically induced damage of human sperm nuclei.

A human sperm activation assay (HSAA) has recently been developed to assess sperm quality and functionality. The HSAA involves incubating lysolecithin-permeabilized sperm in Xenopus laevis ova cytoplasmic extract. Factors in the extract activate sperm nuclei; the activation involves sperm chromatin decondensation, DNA synthesis, and chromatin recondensation. We report that human sperm chemically damaged in vitro by treatment with a reversible crosslinker, ethylene glycolbis(sulfosuccinimidylsuccinate; SEGS), display abnormal chromatin decondensation when analyzed in the HSAA. Less than 20% of SEGS-treated sperm fully decondensed, vs. 97% of control sperm. Chemical reversal of the crosslinks by treatment with 5 microM hydroxylamine restored full decondensation in 76% of treated sperm. These results demonstrate that chemically damaged sperm respond abnormally in the HSAA, and that chemical damage to sperm nuclei can be detected using the HSAA. Thus, there is potential for the HSAA to be used to detect chemical alterations of sperm nuclei from men exposed to environmental toxicants.

Animals↗

Venous thrombosis associated with the placement of peripherally inserted central catheters.

PURPOSE: Peripherally inserted central catheters (PICCs) have become an essential component of the management of an increasing number of patients, including patients who may require hemodialysis. Reported symptomatic venous thrombosis rates associated with PICC lines are based on clinical signs and symptoms and range from 1% to 4%. The purpose of this study is to evaluate the true rate of thrombosis of upper extremity veins after the placement of PICCs and the potential impact on future access in hemodialysis patients. MATERIALS AND METHODS: A retrospective analysis was performed. Patients who had (i) normal findings during initial venography, (ii) PICC placement, and (iii) who underwent subsequent repeated venography were included. Age, sex, vein cannulated, catheter size, location, and incidence of thrombosis were analyzed. RESULTS: Three hundred fifty-four PICCs were placed in 119 patients. Of the 144 extremities, 137 had normal findings during initial venography. Of the 137 extremities, 32 developed thrombosis of the cannulated vein (or central veins) after initial PICC placement (23.3%). When all extremities with multiple PICC lines placed were considered, 52 developed thrombosis, for an overall thrombosis rate of 38%. The incidence of thrombosis by site was cephalic 57%, basilic 14%, and brachial 10%. No significant differences were noted in the rates of thrombosis by age, sex, or catheter size. CONCLUSIONS: There is a relatively high rate of venous thrombosis associated with PICCs, particularly cephalic thrombus. Because of the high rate of thrombosis associated with these catheters, an alternative mode of access should be considered in current or potential hemodialysis patients. All patients with a history of PICC line placement requiring dialysis access should undergo upper extremity venography prior to the placement of permanent access.

Adolescent↗

Solubility and water absorption of orthodontic cements.

Solubility and water absorption of eight orthodontic cements were determined as a function of time. Two brands of BIS-GMA and three brands of acrylic cements ranked about equally in solubility and water absorption. Three brands of polycarboxylate cements were appreciably poorer in these properties.

Absorption↗

Use of Xenopus laevis frog egg extract in diagnosing human male unexplained infertility.

Approximately one in six married couples find themselves involuntarily infertile. This ratio translates to between two and four million U.S. couples. Although numerous tests are available for diagnosing infertility problems, 5-10 percent of all couples who seek medical treatment are diagnosed with unexplained infertility. Several tests are presently available for diagnosing male infertility; however, none of the present procedures test for activation of the sperm nucleus following entry into the fertilized egg, a series of events critical for the entry of the zygote into the developmental program. We have developed an in vitro human sperm activation assay, using Xenopus laevis frog egg extract. When normal human sperm is permeabilized and then mixed with frog egg extract, the sperm nuclei decondense, synthesize DNA, and recondense during a three-hour time course. We have tested this assay's utility in diagnosing previously unexplained infertility. We found that 20 percent of the male infertility patients produced sperm that responded abnormally in the assay (95 percent confidence interval, 4-48 percent; n = 15), while sperm samples from 15 fertile males showed no abnormal responses (p = 0.0112). These preliminary results indicate that the human sperm activation assay may be a useful tool for diagnosing some cases of human infertility.

Animals↗

In vitro drug sensitivity of tumor cells is correlated with drug-induced inhibition of DNA synthesis.

The objective of this study was to develop a rapid in vitro method for predicting the response of human tumors to anticancer drugs. In this study an attempt was made to correlate the drug effects on the relative incorporation of (3H) thymidine (ThdR) into DNA with the sensitivity of tumor cells to that drug. The results of the study indicate that following treatment of the cells with adriamycin (ADR) or 1-(2-chloroethyl)-3-(4-methyl cyclohexyl)-1 nitrosourea (MeCCNU), there was a significant inhibition of DNA synthesis in the drug-sensitive cells. However, the inhibition was relatively small in the drug-resistant cells. Following cytosine arabinoside (Ara-C) treatment, a dramatic recovery in the rate of DNA synthesis was seen in Ara-C-resistant cells but not in cells sensitive to Ara-C. Thus, the method described in this study appears to be capable of distinguishing whether a tumor cell line is sensitive or resistant to a given drug.

Animals↗

Asymmetric mamillary bodies: MR identification.

We report three cases in which there was marked asymmetry of the mamillary bodies, noted on MR in two and at autopsy in the third. Based on its proposed pathogenesis, we suggest that this finding could have value in locating temporal lobe disease in patients with intractable epilepsy.

Adult↗