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Biomedical subjects

D G Martin

Publications and source records attributed to D G Martin.

At least 37 records · Page 2Linked to original sources
PubMed1987

Factors associated with low birthweight in an inner-city population: the role of financial problems.

A case-control study of low birthweight among residents of high risk areas of Alameda County was conducted in 1983. The relation of 13 variables to low birthweight was assessed using a multiple logistic regression analysis. A six-fold increase in the risk of low birthweight was found in association with financial problems during the current pregnancy, controlling for differences in race, certain poor health habits, complications of pregnancy, and several other factors between cases and controls.

Female↗
PubMed1987

Lateralizing brain damage with the Luria-Nebraska Neuropsychological Battery: diagnostic effectiveness as compared to the Halstead-Reitan Neuropsychological Test Battery.

This investigation examined the ability of the Luria-Nebraska Neuropsychological Battery (LNNB) to lateralize brain damage, since substantial statistical and methodological issues have been raised regarding the initial LNNB lateralization validation study. A comparison was then made of the ability of the LNNB and the Halstead-Reitan Neuropsychological Test Battery to lateralize brain damage. Both neuropsychological batteries were administered to 30 predominantly left- or right-hemisphere-damaged subjects (15 in each group) with discriminant analysis classification procedures demonstrating similar, above chance, accuracy in lateralizing cerebral dysfunction. Cross-validation of objective clinical rules designed to aid in LNNB test interpretation resulted in classification of brain damage and lateralization at levels below reported values from the test developer's laboratory. The limited role such simplistic rules have in assessment is discussed, as is the need to evaluate dimensions of test usefulness other than those related to gross diagnostic decisions (e.g., presence or laterality of brain damage) in determining the instrument of choice for clinical neuropsychological practice. More research is recommended to fully define the limits of the clinical utility of the LNNB.

Brain↗
PubMed1986

Plasma viscosity elevations with simulated weightlessness.

Bed rest studies which simulate weightlessness have demonstrated marked changes in the state of hydration of subjects as well as decrements in aerobic capacity. These two phenomena may be linked through increases in blood viscosity which is altered by a loss of free water and which, in turn, influences blood flow needed for aerobic muscular work. This study examines changes in the rheologic properties of blood which attend changes in plasma volume with bed rest in humans and correlates these changes with alterations in aerobic capacity. Eight healthy human subjects were studied on the 6th day of bed rest during two consecutive 10-d bed rest periods separated by a 14-d recovery interval designed to simulate the flight-layover schedule of shuttle astronauts. Plasma viscosity was measured with a Wells-Brookfield viscometer, plasma volume by dye dilution, and maximal aerobic capacity (VO2max) by recumbent cycle ergometry. Bed rest resulted in significant increases in hematocrit and in total plasma protein concentration and fibrinogen concentration, both of which contribute to an elevation in plasma viscosity. The greater than 20% increase in fibrinogen concentration was much greater than could be explained by hemoconcentration. VO2max decreased significantly in the first but not the second bed rest cycle. In many individuals, a decrease in plasma volume and aerobic capacity was coupled with elevated plasma viscosity and hematocrit; however, significant correlations between these variables were lacking. Although significant rheologic perturbations do occur with bed rest, in this study, blood viscosity elevation failed to directly correlate with the reduction in VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Blood viscosity responses to maximal exercise in endurance-trained and sedentary female subjects.

To assess whether the rheological properties of blood might be altered by exercise, we measured whole blood viscosity, plasma viscosity, and its components in healthy female subjects before, immediately after, and 1 h after maximal upright exercise using the Bruce graded exercise protocol. Forty-seven female subjects (15 sedentary, 14 who ran 5-15 miles/wk, and 18 who ran greater than 50 miles/wk), ages 18-43 yr, were evaluated. Whole blood viscosity, measured with a cone and plate viscometer, increased an average of 12.6% with exercise. The increase was greater than can be attributed to the observed 8.9% increase in hematocrit alone due to a coincident increase in plasma protein concentration. However, plasma viscosity did not rise to the degree expected, likely due to a disproportionate observed loss of fibrinogen from the protein pool. These changes were independent of conditioning level or aerobic capacity. In this cross-sectional study, there appears to be no adaptive adjustment in females to physical conditioning that results in changes in blood viscosity.

Adult↗
PubMed1985

CC-1065 transformations.

This report defines the transformations that antitumor antibiotic CC-1065 underwent under basic and acidic conditions. The isolation, purification, characterization, and biological properties of a cyclopropapyrroloindole fragment, and an acidic fragment, PDE-I dimer, from a mild alkaline fragmentation and the phenolic product, AAP, resulting from alkylation of acetic acid by the cyclopropyl function are described.

Antibiotics, Antineoplastic↗
PubMed1985

Evaluation of the zetacrit and zeta sedimentation ratio in dogs.

The Wintrobe erythrocyte sedimentation rate (ESR) has been used in animals and persons as a screening test for inflammatory disease and as a monitor for disease progression in individuals. Now, the zetacrit (ZC) and zeta sedimentation ratio (ZSR) are suggested as suitable rapid laboratory tests to replace the ESR in dogs. In 65 dogs, a strong inverse correlation between ESR and ZC was observed (r = -0.961, P less than 0.05). Significant correlations of similar magnitude between ZC and hematocrit (r = 0.587, P less than 0.05) and ESR and Hct (r = 0.569, P less than 0.05) were observed. In addition, influences of various protein fractions, such as fibrinogen, globulin, and albumin, on the ESR and ZC were evaluated and found to be of similar magnitude. These data indicate that ESR and ZC are equivalent methods for determining erythrocyte sedimentation rates in dogs. A strong correlation (r = 0.900, P less than 0.05) between Wintrobe ESR, adjusted for the effect of Hct (ESRHct), and ZSR was observed. The influence of plasma proteins on ESRHct and ZSR was of similar magnitude. However, a weak yet significant correlation between ESRHct and the microhematocrit remained (r = 0.291, P less than 0.05). Data indicate that the latter more effectively factors out the influence of Hct on sedimentation.

Animals↗
PubMed1984

Conditioning in the unattended left ear.

Two experiments demonstrated that a conditioned emotional response can both be established and arouse responses without awareness in a dichotic paradigm. Right handed male subjects performed a complex verbal task presented to the right ear, while patterns of musical notes were presented to the left ear. For experimental subjects, one of the patterns was always followed by an aversive noise in the left ear; the noises were presented at random times to control subjects. In Study 1, latency of skin potential response to the noise decreased among experimental subjects relative to control subjects, indicating that the critical tone pattern was acting as a CS. Subject awareness was determined through both recall and recognition procedures, and only unaware subjects were used. Study 2 demonstrated the effect more powerfully by showing conditioned responses among experimental subjects on interpolated CS-alone trials and a lack of reportable awareness among all subjects.

Adolescent↗
PubMed1984

Selective forgetting of aversive memories cued in the right hemisphere.

Several writers have suggested that there is selective inhibition of aversive right hemisphere processes from reaching the left hemisphere, thus reducing reportable awareness, although the right hemisphere processes might still affect behavior. Two similar experiments are reported supporting this theory. In the first of three phases, subjects learned a paired associate list to a criterion of one perfect trial. Second, distant associates of some of the words learned in phase 1 were punished. Third, subjects attempted to recall the first word list, with recall cued sometimes in the left visual field and sometimes in the right. Associates of punished words were more likely to be forgotten than control words, when cued in the left visual field so they had to cross from right to left hemisphere to be vocalized. Surprisingly, associates of punished words were remembered better when cued in the right visual field.

Adult↗
PubMed1984

Selective inhibition of vocal reaction time to aversive words in the left visual field.

Four experiments are reported in which subjects vocalized words presented in the visual half-fields in a baseline period. Then two of the words were followed by aversive noise in a punishment phase, and finally, the baseline procedure was repeated. In two studies, as predicted, right handed males' reaction time improved least on words associated with the punished words when they appeared in the left visual field and had to cross from right to left hemisphere to be vocalized. The effect was not found among female subjects in the third study. Finally, the effect was found only among subjects in the highest third on the Repression-Sensitization scale. Taken together, the studies support the notion of selective inhibition of aversive processes that must cross from right to left hemispheres, although individual differences limit the generalizability of this statement.

Adult↗
PubMed1983

Brain laterality and the subliminal perception of facial expression.

Right-handed subjects were presented simultaneously with: (1) a face expressing positive, neutral, or negative affect in the left or right visual field and, (2) the outlines of the face containing visual noise, in the opposite visual field. A range of stimulus presentation durations was used to sample above and below threshold processing. On each trial subjects responded to two forced choice questions: (1) Which side was the face on? and (2) What was the emotion expressed by the face? The results revealed a left visual field advantage for locating the face. There was only suggestive evidence in favour of a right hemisphere superiority in the processing of facial expression per se. The most important finding was that when subjects' performance locating the face represented chance (i.e., there was no reportable awareness of stimulus cues needed to discriminate a face from a nonface), they were significantly above chance identifying the facial expression.

Adult↗
PubMed1980

Inferred natural history of uveal melanoma.

We have observed that the fatality rate of patients with posterior uveal melanomas rapidly increased from a very low rate prior to enucleation to a maximum of 8% per year during the second year after enucleation. These data suggest to us that events related to enucleation have a deleterious effect on survival, and we have postulated that these events are either the iatrogenic dissemination of tumor cells or an adverse effect on the immune-defense system, or both. Others have proposed that the relationship between enucleation and increased mortality is only happenstance. They would attribute the onset of symptoms to the rapid growth of the malignant tumor and thus claim that this brings the patient to enucleation soon after the tumor becomes malignant. We have studied 2105 cases on file in the REgistry of Ophthalmic Pathology and have found that enucleation was not always performed shortly after the onset of visual disturbance. In one third of the cases, enucleation was delayed until onset oment was not obtained until the tumor measured larger than 15 mm in diameter. Using Zelen's method to infer the natural history of uveal melanoma, we found that the mean time it took for a small tumor (less than 10 mm in diameter) to become a large tumor (greater than 15 mm) was approximately 7 years. The average age of patients treated for medium-sized tumors was 5 years less than that of patients treated for larger tumors. This is interpreted as evidence of an average delay of 5 years in the treatment of large melanomas. If this delay is taken into consideration, then the patients treated with medium-sized tumors had a worse survival during the first 7 years than did patients whose treatment was delayed until the tumor became large. After the seventh year, however, the survival was better. These findings support our hypothesis that the postoperative increase in mortality during the first several years, particularly among patients with tumors of medium size, was related to enucleation.

Actuarial Analysis↗