PubMed Health⌕ Search

Biomedical subjects

F G Martin

Publications and source records attributed to F G Martin.

At least 37 records · Page 2Linked to original sources
PubMed1992

Circuit analysis of transmembrane voltage relationships in V-ATPase-coupled ion movements.

The concept of electrical circuit analysis is extended to include components found in membrane ionic transport systems. As in classical electrical equivalent circuits, resistors and capacitors are used to represent ion channels and the membrane capacitances, respectively; batteries represent energy sources driven by chemical reactions. In the extensions proposed, energy stored in various ionic concentrations is treated as charges on compartmental capacitors; symporters and antiporters are treated as energy-coupling devices analogous to transformers in alternating current electrical circuits. Pumps are shown to be special cases of porters in which the input circuit derives its energy from a chemical reaction. Using these components, circuit diagrams are drawn for several examples of membrane ion transport systems. By applying appropriate circuit analysis techniques, these diagrams facilitate the quantitative description of the energy distributions throughout the system.

Adenosine Triphosphatases↗
PubMed1991

Prepartum and peripartum reproductive performance of dairy heifers freshening at young ages.

Reproductive performance of five breeds (81% Holstein or Jersey) in the Florida Agricultural Experiment Station herd was evaluated from data collected over 20 yr. Data represented 1144 parturitions after gestations greater than 250 d with all twin births excluded. Number of services per conception was not affected by age at first insemination. Mean age of exposure to first service was 414 d; mean age at first parturition was 25.8 mo. Overall, 39.7% of heifers calved at 23 mo or less. Intermediate ages, 24 to 27 mo, comprised 33.9% of heifers, whereas 26.4% of heifers calved at greater than or equal to 28 mo. Overall incidences of problems at parturition were retained fetal membranes, 3.6%; dystocia, 3.8%; metritis, 10.5%; and stillbirth, 11.5%. Frequencies of stillbirth and retained fetal membranes apparently were not affected by age, but metritis increased linearly with age at first parturition. Holsteins experience higher incidences of all problems than did Jerseys. Heritability (from paternal half-sib correlation) of birth weights and gestation lengths were .31 and .24; genetic correlation was .14. Heritabilities of occurrence of stillbirth, retained fetal membranes, metritis, and dystocia were negative and considered to be 0. Heritabilities of age at first service, days from first service to conception, number of services, and age at first parturition were .22, .11, .05, and .43. Dairy producers can consider reducing age at first parturition to at least 22 mo, under environmental and management conditions of this study, without increased frequencies of problems at parturition.

Age Factors↗
PubMed1990

Effects of stage of lactation and pregnancy and their interactions on milk yield and constituents.

Effects of stage of lactation and pregnancy and their interactions on 17 milk yield and constituent traits of Holsteins and Jerseys were studied. Data were 11,120 Jersey and 11,092 Holstein daily milk samples. After adjustment for all other known and systematic genetic and environmental effects, stage of lactation influenced all traits and accounted for 11.8 to 26.3% of variation in yields and .2 to 9.9% in percentages. In general, yields declined and percentages increased after about 3 mo of lactation. Chloride percentage showed an initial decline and then a rise after 2 mo. Stage of pregnancy accounted for small but significant variation in most traits; variation was .2 to .4% and less than .1 to 3.0% in yields and percentages for Holsteins, and less than .1 to .2% and .1 to 1.1% for Jerseys. Interactions between stage of lactation and pregnancy were investigated by response surface methodology and found to be very small.

Animals↗
PubMed1988

Interactions of climatic factors affecting milk yield and composition.

Objectives were to evaluate effects of interactions of maximum temperature, minimum relative humidity, and solar radiation on milk yield and constituent traits. Effects of climate variables and their interactions were significant but small in most cases. Second order regression models were developed for several variables. Six were examined in detail: Holstein and Jersey milk yields, Holstein fat and Feulgen-DNA reflectance percent, and Jersey protein percent and yield. Maximum temperature had greatest influence on each response, followed by minimum relative humidity and solar radiation. Optimum conditions for milk production were at maximum temperatures below 19.4 degrees C, increasing solar radiation, and minimum relative humidity between 33.4 and 78.2% (cool sunny days, moderate humidity). Maximum Holstein fat percent of 3.5% was predicted for maximum temperatures below 30.8 degrees C, minimum relative humidity below 89%, and solar radiation below 109 Langleys; actual mean Holstein fat percent was 3.35%. Optimum climatic conditions for Jersey protein percent were at maximum temperature of 10.6 degrees C with solar radiation at 300 Langleys and relative humidity at 16% (cool sunny days, low humidity). Because noteworthy interactions existed between climate effects, response surface methodology was suitable for determining optimum climatic conditions for milk production.

Animals↗
PubMed1988

Ingestion of grapefruit lowers elevated hematocrits in human subjects.

This study was based on in vitro observations that naringin isolated from grapefruit induced red cell aggregation and evidence that clumped red cells are removed from the circulation by phagocytosis. The effect on hematocrits of adding grapefruit to the daily diet was determined using 36 human subjects (12 F, 24 M) over a 42-day study. The hematocrits ranged from 36.5 to 55.8% at the start and 38.8% to 49.2% at the end of the study. There was a differential effect on the hematocrit. The largest decreases occurred at the highest hematocrits and the effect decreased on the intermediate hematocrits; however, the low hematocrits increased. There was no significant difference between ingesting 1/2 or 1 grapefruit per day but a decrease in hematocrit due to ingestion of grapefruit was statistically significant at the p less than 0.01 level.

Adult↗
PubMed1987

Canine cardiovascular responses to endotracheally and intravenously administered atropine, isoproterenol, and propranolol.

This study compared canine cardiovascular responses observed after endotracheally administered atropine, isoproterenol, and propranolol to those observed following IV administration. Acetylcholine and isoproterenol dose response curves for arterial pressures and heart rate were established following IV boluses of each drug. Once the dose response curves were established, atropine and propranolol were administered endotracheally and intravenously in different groups to alter the established dose response curves. The time required for endotracheally and intravenously administered atropine and propranolol to inhibit 50% of the mean arterial pressure response following an IV infusion of acetylcholine and isoproterenol, respectively, was determined. Atropine and propranolol administered by either route significantly altered the arterial pressure response to acetylcholine and isoproterenol (P less than .05), respectively. Atropine altered the heart rate response to acetylcholine when administered by either route (P less than .05). IV-administered propranolol altered the heart rate response to isoproterenol (P less than .05); endotracheally administered propranolol did not. Atropine administered IV inhibited 50% of the mean arterial pressure response during an acetylcholine infusion within 21 seconds, and within 48 seconds following endotracheal administration. Propranolol administered intravenously inhibited 50% of the mean arterial pressure response during an isoproterenol infusion within 23 seconds, and within 49 seconds following endotracheal administration. The arterial pressure and heart rate responses immediately following endotracheally and intravenously administered isoproterenol also were measured and compared. The arterial pressure and heart rate responses after endotracheally administered isoproterenol were much less than those following IV administration (P less than .005). In dogs the pharmacological effects following endotracheally and intravenously administered atropine and propranolol are similar, while the effects of endotracheally and intravenously administered isoproterenol differ greatly.

Animals↗
PubMed1985

Effects of relative humidity, maximum and minimum temperature, pregnancy, and stage of lactation on milk composition and yield.

Composite monthly single-day milk samples from the Florida Agricultural Experiment Station dairy herd 1959 to 1974 were analyzed for composition. Data were 22, 972 observations on five dairy breeds, but major statistical analyses were limited to Jerseys and Holsteins. Minimum relative humidity and maximum and minimum temperatures on day of evening sample were associated with 1.6 to 5.6% of variability within lactation (range for two breeds) of milk and milk constituent yields and 1.1 to 16.5% of constituent percentages. Yields of milk and constituents of the Holsteins seemed more sensitive to climatic variation than did Jersey, but Jersey constituent percentages were more sensitive. Yields were affected only slightly by increasing maximum daily temperatures from 8 to 29 degrees C but declined rapidly at greater than 29 degrees C; fat and protein percentages declined from 8 to 37 degrees C, whereas chloride content increased above 21 degrees C. Stage of lactation and pregnancy effects accounted for about 50% of the variability of yields and 3 to 23% of percentages. Effects were detected also for chloride and acidity percentages, specific gravity, and ratios solids-not-fat to fat and protein to fat.

Animals↗
PubMed1983

Interaction of cyclazocine and the sympathetic nervous system.

Cyclazocine, a benzomorphan derivative narcotic agonist-antagonist, reduced the uptake of tritiated norepinephrine and reduced the recovery of [3H]3,4-dihydroxymandelic acid, but did not significantly alter the recovery of [3H]normetanephrine in the rat heart in vivo. Cyclazocine also reduced endogenous levels of norepinephrine in the rat heart. Comparatively, desipramine reduced the uptake of [3H]norepinephrine, the recovery of [3H]3,4-dihydroxymandelic acid, and the recovery of [3H]normetanephrine in the rat heart in vivo. Further, cyclazocine added to the perfusion medium or administered systemically reduced the uptake of radiolabeled norepinephrine by the isolated rat heart. The cyclazocine-induced decrease in the accumulation of [3H]norepinephrine in the rat heart in vivo and in vitro presumably is due to an alteration of sympathetic function through the inhibition of neuronal uptake. It is further suggested that cyclazocine has other actions on the sympathetic nervous system, such as promoting neurotransmitter release.

Animals↗
PubMed1983

An ultrastructural morphometric study of the papillary muscle of the right ventricle of the cat.

The papillary muscle of the cat heart's right ventricle has not been studied previously with quantitative ultrastructural techniques despite its wide use for functional studies. This tissue was perfusion-fixed, processed for electron microscopy, and morphometric techniques were used to assess the ultrastructural characteristics of the papillary muscle as well as the working myocardial cells. The results of this study were that 73.5% of the papillary muscle was composed of muscle cells, 9.7% of blood vessels, and the remainder of interstitial connective tissue. In the muscle cell the volume fraction of mitochondria was 17.3%, that of myofibrils was 49.8%, and that of the nucleus was 2.0%. The mitochondria to myofibrils ratio was 0.36 and the surface to volume ratio was 0.309. In a quantitative ultrastructural comparison of perfusion and immersion fixed tissue it was found that significant differences in the volume density of the blood vessel lumen existed between the two groups. In addition, there were significant differences in the volume fraction of mitochondria and nucleus between perfusion-fixed and immersion-fixed muscle cells. A concurrent significant decrease between the two groups was also found for the ratio of mitochondria to myofibrils. The perfusion-fixed tissue can be considered to provide only normal baseline data for the papillary muscle of the right ventricle. These data are important as they can be used in future structure-function studies on normal and pathological heart tissue.

Animals↗
PubMed1983

Potassium measurements in the extracellular spaces of normal and failing cat myocardium.

After periods of quiescence, papillary muscles and trabeculae from normal and hypertrophied-failing cat hearts were subjected to ionic stress induced by stimulation (drive) at different frequencies. Patterns of change in extracellular potassium concentration were measured using ion-selective microelectrodes and were shown to be significantly different in certain key parameters. In both types of tissue, extracellular potassium activity initially increased from the level in the bathing medium, reached a peak, and then returned toward the original levels. However, the time for this to occur was significantly longer in the hypertrophied-failing muscles than in the normal controls. Also, after more than 5 min of drive, the potassium activity in the extracellular spaces was significantly higher in the hypertrophied-failing tissue than in the normal tissue. The results of these experiments indicate that there may be quantitative differences between normal and hypertrophied-failing cardiac muscles with regard to the regulation of ionic balance.

Animals↗
PubMed1983

Vital statistics and reasons for disposal of United States and Canadian artificial insemination dairy sires.

Vital statistics were evaluated for artificial insemination sires leaving service during 1939 through 1974. Data consisted of 11,704 sires of six breeds. The major cause for leaving service was reproductive failure at a frequency of 32.5%; next ranked was undesirable characteristics of offspring with a frequency of 20.7%. Overall culling rate for low yields of daughters was 14.8%, but after 1965 this cause accounted for about 30%. Mean life span was 3.4 yr with small differences among years. Breed differences were detected for service life and causes for leaving service. Modifications of classic life table techniques are needed to reflect entry of sires into service at various ages and evaluation of vital statistics subsequent to 1974.

Age Factors↗
PubMed1982

Mineral status of llamas and sheep in the Bolivian Altiplano.

An experiment was conducted in the highlands (Altiplano) of Bolivia to establish the specific mineral status for growing llamas compared to sheep grazing unfertilized, native pastures. Animal tissues (plasma, liver and bone), forage and soil samples were collected during the wet and dry seasons and analyzed for mineral contents. During the wet season, forages were higher (P less than 0.05) in Ca, K, Fe and protein. Percent borderline to deficient forage concentrations during the wet and dry seasons, respectively, were found as follows: protein (less than 7.0%) 20 and 53; CCa (less than 0.30%) 10 and 40; Cu (less than 5 ppm) 20 and 47; K (less than 0.5%) 10 and 20; Mg (less than 0.08%) 10 and 20; Na (less than 0.1%) 30 and 69; P (less than 0.25%) 100 and 100; Zn (less than 30 ppm) 60 and 80; and Se (less than 0.1 ppm) 90 and 93% of the total forages, respectively. Concentrations of liver Mg, Co, Mn, Mo, Se and Zn, plasma Mg and Cu and rib (percent ash) Ca, Mg and P were all higher (P less than 0.05) during the wet than in the dry season. Compared to llamas, sheep had higher (P les than 0.05) concentrations of plasma Ca, Cu, Fe and Zn, rib (milligram/milliliter) P, Mg and Zn and liver Fe, but lower (P less than 0.05) concentrations of liver Co, Cu, Mn and MO. On the basis of forage and animal tissue analyses, the nutrients protein, P, Ca, Zn, Na and Se would be insufficient for optimum production of grazing livestock in the high plains of Bolivia.

Animal Feed↗
PubMed1982

Evaluating the nutritional status of beef cattle herds from four soil order regions of Florida. I. Macroelements, protein, carotene, vitamins A and E, hemoglobin and hematocrit.

The nutrient status of grazing beef cattle from four selected soil order regions of Florida was examined. Liver, blood, hair and feces samples from 14 heifers and 14 cows, plus forage samples, were collected during two periods of the year from nine ranches located in four different regions. Soil samples were collected during one period. The soil order regions were the Histosol (southeast), Spodosol (southwest), Entisol (central) and Ultisol (northwest). Mean forage P values were higher (P less than .05) in the wet season, while mean hair P levels were higher (P less than .05) during the dry season. Mean forage, plasma, liver and hair Mg values were higher (P less than .05) in the wet season. Plasma vitamin E, liver vitamin A and forage carotene levels were higher (P less than .05) during the wet season. Mean forage P content was deficient (less than .25%) during both seasons and varied from .10% in the dry season to .16% during the wet season. Mean forage Mg (less than .18%) and K (less than .60%) concentrations were deficient in the dry season. Forage protein was deficient (less than 7.0%) in five of seven ranches during the dry season. Extractable soil Ca, exchangeable soil Ca, Mn, Al, H+, soil organic matter and effective cation exchange capacity were higher (P less than .05) in the Histosol region. Extractable soil K was low (60 ppm) in all regions, except the northwest. Forage P was critical (less than .25%) during the dry season in all regions and varied from .08 to .15%, while plasma P was deficient (4.5 mg/100 ml) in animals from the southeast during the dry season only.

Animals↗
PubMed1982

Evaluating the nutritional status of beef cattle herds from four soil order regions of Florida. II. Trace minerals.

An experiment was conducted to determine the trace mineral status of grazing cattle from four selected soil type regions in Florida. Animal tissue, forage and soil samples were collected during the wet (September-October) and dry (February-March) seasons from nine ranches located in four different regions. On the basis of reported critical forage levels, mean forage Co (less than .1 ppm), Zn (less than 30 ppm) and Se (less than .1 ppm) and liver and hair Se (less than .25 ppm), were low during both seasons. Soil Se (less than .50 ppm) and extractable soil Zn (less than 1.5 ppm) were low in all regions except the southeast. Mean forage Se was low in all regions. Of all animals studied in the wet season, 36 and 32% had low liver Cu (less than 75 ppm) and Se (less than .25 ppm) concentrations, respectively. In the dry season, 20 and 39% of the animals had low liver Cu and Se concentrations, respectively. Hair Se was low (less than .25 ppm) in 90% of the samples during the wet season and in 100% during the dry season. During the wet season, forage Zn, Mn, Co and Se were low in 89, 26, 63 and 84% of the samples, respectively, while extractable (double acid) Zn, Mn, Co and total Se were low in 57, 79, 63 and 100% of the soils, respectively. In the dry season, 80, 20, 40 and 80% of forages were low in Zn, Mn, Co and Se, respectively. Of the seven trace minerals studied, Se and Zn are most likely to be deficient, with Co and Cu insufficiency probable in selected areas.

Animals↗
PubMed1978

The process of development of interagency relationships.

Seven parameters of an interagency relationship were examined for their importance to the process and perceived effectiveness of the relationships between a new community agency and seven established agencies. Perceptions of performance of the new agency on these seven parameters changed over time, primarily in a positive direction. In the first 6 months of a relationship, the quality of planning for projects was correlated with perceived effectiveness. When a relationship was 12 to 18 months old, clarity of goals and of activities, presentation of the agency's mission, the agency's resources, and the agency's communications were related to perceived effectiveness. Implications for the development of interagency relations are discussed.

Child↗
PubMed1977

Effect of pentazocine on pressor responses of epinephrine and levarterenol.

In rats anesthetized with pentobarbital, pentazocine potentiated the pressor response of two exogenous amines, epinephrine and levarterenol. Although the mechanism for the pentazocine-induced potentiation of the pressor amines has not been proven, it is speculated that pentazocine may increase the blood pressure response of certain amines by interacting with the sympathetic nervous system.

Animals↗
PubMed1975

Transient renal dysfunction associated with acute pyelonephritis of pregnancy.

Endogenous creatinine clearance was measured in 220 pregnant women with acute pyelonephritis and the results compared to data obtained from 167 pregnant control patients without acute pyelonephritis. These data showed that an appreciable number of patients with pyelonephritis occurring during pregnancy demonstrated a transient but definite diminution in renal function during the acute attack. Causes of this temporary renal dysfunction are discussed.

Creatinine↗