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Biomedical subjects

D L Holmes

Publications and source records attributed to D L Holmes.

30 records · Page 2Linked to original sources

Electrophoresis of DNA in oriented agarose gels.

Oriented agarose gels were prepared by applying an electric field to molten agarose while it was solidifying. Immediately afterwards, DNA samples were applied to the gel and electrophoresed in a constant unidirectional electric field. Regardless of whether the orienting field was applied parallel or perpendicular to the eventual direction of electrophoresis, the mobilities of linear and supercoiled DNA molecules were either faster (80% of the time) or slower (20% of the time) than observed in control, unoriented gels run simultaneously. The difference in mobility in the oriented gel (whether faster or slower) usually increased with increasing DNA molecular weight and increasing voltage applied to orient the agarose matrix. In perpendicularly oriented gels linear DNA fragments traveled in lanes skewed toward the side of the gel; supercoiled DNA molecules traveled in straight lanes. If the orienting voltage was applied parallel to the direction of electrophoresis, both linear and supercoiled DNA molecules migrated in straight lanes. These effects were observed in gels cast from different types of agarose, using various agarose concentrations and two different running buffers, and were observed both with and without ethidium bromide incorporated in the gel. Similar results were observed if the agarose was allowed to solidify first, and the orienting electric field was then applied to the gel for several hours before the DNA samples were added and electrophoresed. The results suggest that the agarose matrix can be oriented by electric fields applied to the gel before and probably during electrophoresis, and that orientation of the matrix affects the mobility and direction of migration of DNA molecules. The skewed lanes observed in the perpendicularly oriented gels suggest that pores or channels can be created in the matrix by application of an electric field. The oriented matrix becomes randomized with time, because DNA fragments in oriented and unoriented gels migrated in straight lanes with identical velocities 24 hours later.

DNA↗

Inflammation due to surgical glove powders in the rabbit eye.

Inflammatory anterior chamber reactions secondary to contamination by talc, absorbable dusting powder (ADP), and a combination of these powders were studied in rabbits. These common surgical glove powders were introduced into the anterior chambers of 30 animals, and structural changes were observed on days 1 and 3, and at weeks 1, 4, 8, and 12. Our findings indicate that the combination of talc and ADP causes a substantially more acute inflammatory reaction than either agent used individually. Chronic granulomatous inflammation was more severe in the group that received ADP plus talc than in the group that received talc only.

Animals↗

Physiological characteristics of elite sport parachutists.

The physiological characteristics of 10 male elite sport parachutists (31.6 +/- 3.69 years of age) were determined and compared to 10 male non-sport parachutist controls (30.2 +/- 4.31 years) and other selected elite athletes. The typical sport parachutist was a highly educated (16.4 +/- 2.41 years), first born (9 out of 10), and, more often than not, single individual. During their mean 10.8 years of sport parachuting, these individuals made an average total number of 1,950 jumps (range 980 to 3,100) with a mean of 237.5 jumps during each of the last three years. Mean total free fall time was 22 h and 40 min. Compared to the non-sport parachutist control group, the elite sport parachutists were significantly higher (p less than 0.05) in aerobic power (47.4 +/- 9.04 vs. 37.2 +/- 4.67 ml X kg-1 X min-1), vital capacity (5.27 +/- 0.49 vs. 5.05 +/- 0.31 L), maximum heart rate (203.2 +/- 9.2 vs. 190.1 +/- 7.4 bpm), and back hyperextension flexibility (21.12 +/- 4.1 vs. 18.41 +/- 2.4 in). The elite sport parachutist were also significantly lower (p less than 0.05) in relative (%) body fat when compared to the control group (15.7 +/- 4.51 vs. 20.1 +/- 2.12%). The two groups were not significantly different (p greater than 0.05) with respect to resting heart rate, absolute body weight, dominant hand-grip strength, or lower back/hamstring flexibility as measured by the sit-and-reach test. Regarding somatotype, the elite sport parachutist can be classified as a balanced mesomorph. Compared to other selected elite athletes, the sport parachutists were lower in aerobic power and higher in relative body fat, yet with a summation of triceps, suprailiac, and abdominal skinfolds in the acceptable range for male athletes. The elite sport parachutists were approximately mid-range in absolute body weight and lower back/hamstring flexibility when compared to other selected elite athletes. Based on the findings of this study, there is evidence to suggest that some form of regular aerobic exercise along with a stretching and flexibility program is advisable for those individuals considering frequent participation and desiring peak performance in sport parachuting.

Adult↗

Searching for multiple targets simultaneously: is it really possible?

In an attempt to clarify the findings of Neisser and his associates with respect to parallel processing of multiple target items in a visual search task, subjects were tested in a multiple-target search situation in which the various target sets were not nested. 20 sessions were run for each subject with 12 trials per day. The targets used were geometric forms, allowing for manipulation of the number of features in each form. The results do not confirm those of Neisser, in fact, the interaction of session x target-set size was in a direction opposite to that predicted by a parallel preattentive processing may in fact have reflected a tendency for subjects to scan for a master set of targets, regardless of which subset of that set was actually present on a given set.

Adult↗

Use of constant target sets in visual search tasks.

54 subjects participated in a visual scanning study in which each subject was provided with only a single target set (of 1, 2, 4, 6, 8, or 10 letters in length). Eight sessions of 30 trials each were completed for each subject. Although there were slight differences in the rate at which performance improved over trials, this was not systematically related to size of target set. Moreover, even in the last session, there were large differences in performance in the different target sets. These findings suggest that Neisser's evidence for parallel preattentive processing in such tasks may have been confounded by his use of nested target sets and a within-subject design.

Adult↗

An evaluation of the use of spelling error analysis in the diagnosis of reading disabilities.

This study examined whether significant differences could be observed in types of errors made by normal versus retarded readers (fifth graders) on the WRAT spelling test. Although researchers have reported high numbers of certain types of errors, such as reversals, this study revealed that the proportion of errors attributed to any particular error type is virtually identical for both normal and retarded readers. Retarded readers were thus shown to be unlike normal readers in the number of errors committed but like normal readers in the types of errors committed.

Child↗

Site specific 1:1 opioid:albumin conjugate with in vitro activity and long in vivo duration.

A site-specific 1:1 dynorphin A-(1-13)-NH(2) derivative conjugated specifically to Cys 34 on human serum albumin (CCI-1035) was shown to be an opioid receptor agonist in vitro and to be a long lasting antinociceptive agent when administered intravenously to mice as assessed by an acetic acid writhing assay. When 10 micromol/kg of CCI-1035 was administered to mice, rapid antinociception was observed within 5 min following intravenous bolus injection and was sustained beyond 8 h. Antinociceptive activity was absent in a heat induced pain model using a mouse tail-flick assay. This finding represents the first report of a 1:1 albumin opioid conjugate retaining potent in vivo activity equal to or greater than dynorphin A, accompanied by a dramatic extension in duration of action. This novel site-specific bioconjugation technology produces an agent that may be useful for peripheral pain therapy.

Amino Acid Sequence↗

N-(3-azidophenyl)-N-methyl-N'-([4-1H]- and [4-3H]-1-naphthyl)guanidine. A potent and selective ligand designed as a photoaffinity label for the phencyclidine site of the N-methyl-D-aspartate receptor.

A novel radiolabeled photoaffinity ligand has been synthesized for the phencyclidine (PCP) site of the N-methyl-D-aspartate (NMDA) receptor. N-(3-Azidophenyl)-N-methyl-N'-([4-3H]-1-naphthyl)guanidine (13) was prepared with a specific activity of 25 Ci/mmol by diazotization of N-(3-aminophenyl)-N-methyl-N'-([4-3H]-1-naphthyl)guanidine (12) followed by treatment with sodium azide. Guanidine 12 was obtained by catalytic tritiation of N-(4-bromo-1-naphthyl)-N'-methyl-N'-(3-nitrophenyl)guanidine (11). The nontritiated analog 5 of 13 was prepared beginning with N-methyl-N'-1-naphthyl-N-(3-nitrophenyl)guanidine (9). The guanidines 9 and 11 were prepared in moderate yield by the aluminum chloride-catalyzed reaction of N-methyl-3-nitroaniline hydrochloride with 1-naphthylcyanamide and 4-bromo-1-naphthylcyanamide, respectively. Azide 5 showed high selectivity and affinity (IC50 = 100 nM vs [3H]MK801; 3000 nM vs [3H]ditolylguanidine) for the PCP site of the NMDA receptor in guinea pig brain homogenate. Photolabeling experiments with 13, however, failed to radiolabel a significant amount of receptor polypeptide.

Affinity Labels↗