Search PubMed⌕ Search

Biomedical subjects

D Richardson

Publications and source records attributed to D Richardson.

At least 199 records · Page 11Linked to original sources
PubMed1987

Prospective evaluation of a risk scoring system for predicting preterm delivery in black inner city women.

Nine percent of United States births are preterm. The ability to efficiently identify women destined to deliver before term would enable obstetricians to initiate early intervention. The Papiernik-Creasy risk scoring system is being extensively applied for this purpose, without prospective validation in this country. We evaluated prospectively its ability to predict high risk women in a black inner city population, when applied once early in pregnancy. The system, based on social, past medical, and current pregnancy problems, failed to identify at-risk patients. Adjusting the score cutoff and reweighting factors with discriminate analysis did not improve the predictive value. Analysis of an additional 60 social, demographic, and medical factors failed to produce a useful alternative risk assessment tool. We suggest that risk scoring systems such as these may not be helpful in socioeconomically at-risk populations.

Adult↗
PubMed1986

Relative effects of static muscle contraction on digital artery and nailfold capillary blood flow velocities.

Previous studies have shown that a decrease in blood flow to the finger is not necessarily accompanied by a corresponding change of blood flow in nailfold capillaries. The purpose of this study was to determine if nailfold capillary blood flow remains relatively stable during a decrease in finger blood flow induced by muscle contractions. Four male subjects 20 to 30 years of age exerted 2-min periods of static calf muscle contraction at levels of 7.5, 15, 30, and 45% of their maximum voluntary contractile force (MVC) while systemic blood pressure (BP), and flow velocities in the digital artery (VEL-A) and nailfold capillaries (VEL-C) were measured by, respectively, Doppler ultrasound and video densitometry. Each subject repeated the series five times. There was a significant linear decrease in VEL-A with increasing force of contraction for each subject individually (P less than or equal to 0.009) and for the group as a whole (P less than or equal to 0.0001); whereas VEL-C did not significantly change during muscle contraction. These results indicate that the initial cutaneous constrictor response in the finger during the onset of leg muscle exercise is not reflected to the nailfold capillaries.

Adult↗
PubMed1986

Using a business plan to develop a freestanding radiology center.

Physicians, hospitals and investors are closely scrutinizing the market for freestanding diagnostic and therapeutic centers. Developing a center's business plan can be a critical first step for physicians to gauge the profitability of a new project. Elements of a plan include: volume projections, referral issues, regulatory environment, financial and performance indicators, accountability, time frames and a marketing plan.

Ambulatory Care Facilities↗
PubMed1985

Can preterm deliveries be prevented?

Our hospital serves poor, inner-city women who have a 17% preterm delivery rate. Middle-class women in San Francisco at high risk for preterm delivery have benefited from an antepartum program which emphasized patient education and close follow-up. Using a controlled, randomized design, we are investigating the impact of similar interventions. Patients determined to be at high risk before 18 weeks' gestation on the basis of the Creasy system are randomly assigned to the Preterm Labor Prevention Clinic or serve as high-risk controls. Sixty-four women assigned to the Preterm Labor Prevention Clinic and 68 high-risk control women have been delivered of their infants. No significant differences were noted for the percentages of preterm infants, mean gestational age, or birth weight. Preterm rupture of the membranes accounted for 40% of preterm deliveries in all high-risk patients. Thirty percent of preterm births were indicated for maternal or fetal reasons. The remaining 30% represented failure of tocolytic therapy.

Birth Weight↗
PubMed1985

Effects of ischemia on capillary density and flow velocity in nailfolds of human toes.

The purpose of this study was to investigate reactive hyperemia in the capillary network of human skin in terms of the flow per capillary and the density of flow-active capillaries. Seventeen male subjects 20 to 40 years of age were seated with their right foot placed on the stage of a Leitz epi-ilumination microscope such that the nailfold capillary field in their large toes could be viewed. These vessels were video taped while flow velocity in the right posterior tibial artery was recorded via Doppler ultrasound at rest, then following a 45-sec period of arterial occlusion to the foot. Subsequent to experimentation flow velocity in single nailfold capillaries was measured via video densitometry and the number of flow-active capillaries in the field of view were counted. Following the release of arterial occlusion arterial flow velocity increased 142% above rest, the velocity in single capillaries increased by 54%, and the density of flow-active capillaries, as identified by the presence of red cells, decreased by 37%. The fact that capillary flow velocity increased to a lesser degree than arterial velocity during reactive hyperemia vis-a-vis a decrease in the number of flow-active capillaries indicates that ischemia to the foot elicits a smaller dilatory effect in vascular elements controlling blood flow to the superficial cutaneous region of the toe as compared to other regional vascular networks.

Adult↗
PubMed1985

Amniostat FLM: a new technique for detection of phosphatidylglycerol in amniotic fluid.

Amniostat-FLM (AFLM) is an immunologic semi-quantitative slide agglutination test for determining the presence of phosphatidylglycerol (PG) in amniotic fluid. We analyzed 178 samples for the presence of PG by both AFLM and our standard thin-layer chromatographic technique (TLC). Both tests agreed in 135 of 178 cases. All fluids with a mature AFLM had PG detected by TLC assay. All of the 43 discordant samples were classified as immature by AFLM although PG was present by TLC. Among the 151 patients who delivered within 72 hours of amniocentesis, 17 cases of respiratory distress syndrome (RDS) occurred. All were correctly predicted by immature tests. However, an immature AFLM was associated with RDS in only 21% of cases (11/53) while 37% of cases (17/46) with an immature TLC test resulted in neonates with RDS. We conclude that the AFLM is a very simple, rapid, and sensitive test for identifying infants who will develop RDS but is less specific than the TLC assay. Though a mature AFLM will predict fetal pulmonary maturity, an immature result should be confirmed by thin-layer chromatographic analysis.

Agglutination Tests↗
PubMed1985

Male violence toward females: victim and aggressor variables.

The present study focused on the effects of two variables that have been proposed as determinants of male violence toward female targets in American society. One target variable, verbal attack, and one aggressor variable, masculine performance, were manipulated. Forty male research participants competed in a reaction-time task with a female confederate who had previously criticized them or remained silent when the males' performance on a physical strength task appeared to be average or considerably below the norms for male performance. The significant interaction between the two variables indicated that inhibitions against harming females were reduced when the male performed poorly on a masculine task in the presence of a female who criticized his performance. Results are discussed in terms of their relevance to control and understanding of male-to-female aggression in the natural ecology.

Achievement↗
PubMed1985

The effect of chronic and acyclic elevation of circulating androstenedione or estrone concentrations on ovarian function in the rhesus monkey.

The concept that chronically elevated blood androstenedione concentrations increase the incidence of anovulation in the primate and that acyclic elevated basal blood androgen and/or estrogen concentrations cause abnormal gonadotropin secretion was studied. Regularly menstruating female rhesus monkeys were implanted sc with Silastic tubing filled with androstenedione or estrone and compared with controls. Androstenedione implants increased the serum androstenedione concentrations from 1.6 +/- 0.1 (SE) ng/ml to 6.30 +/- 0.27 ng/ml. By peripheral conversion the testosterone concentration increased from control values of 279 +/- 10 (SE) pg/ml to 1280 +/- 41 pg/ml. The testosterone concentration in the estrone-treated monkeys was 247 +/- 9.7 pg/ml. The estrone concentrations were: controls, 63.2 +/- 3.1 (SE) pg/ml; androstenedione-treated monkeys, 63.2 +/- 3.1 pg/ml; and estrone-treated animals, 150 +/- 5.3 pg/ml. The corresponding estradiol concentrations were: control animals, 35.1 +/- 2.1 (SE) pg/ml; androstenedione animals, 30.9 +/- 1.8 pg/ml; and estrone-treated monkeys, 65.7 +/- 3.9 pg/ml. There was no difference in the morning serum cortisol concentrations between any of the three groups or between ovulatory or anovulatory months. The chronic elevation of either androstenedione or estrone caused an increased incidence of anovulation compared with the controls. Increased estrogen concentrations caused increased anovulation during both summer and winter months; however, increased androgen concentrations caused increased anovulation only during the summer months. However, LH concentrations were unaffected in either group but were lower during anovulation months in all three groups. An LH or FSH surge followed an estradiol bolus in three of four control animals and four of six androstenedione-treated but none of the estrone-treated monkeys. Histological examination of ovarian biopsies demonstrated thickening of the tunica albuginea ovarii in androgen-treated ovaries and an apparent increased number of atretic follicles. Corpora lutea were absent in the ovaries of the estrogen-treated monkeys, but otherwise these ovaries were similar to those of controls. It is concluded that chronic acyclic elevation of blood androstenedione (and resultant testosterone) increases seasonal anovulation in the rhesus monkey. Increased blood estrone (and resultant estradiol) leads to almost complete anovulation throughout the year and renders the central nervous system-pituitary axis insensitive to positive feedback effect of estradiol. Neither treatment caused an increase in basal LH concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Cortex↗
PubMed1985

Measurement of portal and hepatic blood flows using a modified method for surgical placement of catheters in the major splanchnic vessels of sheep.

A modified catheterization and para-aminohippurate dye dilution technique was used to measure portal and hepatic blood flows in sheep. Blood flows (mean +/- 1SD) for 7 healthy sheep were 1.54 +/- 0.71 L/min and 1.98 +/- 0.75 L/min for portal and hepatic flows, respectively. Blood flow measurement was facilitated when dye injection rates produced blood para-aminohippurate acid concentrations greater than 15 mg/L. Uniform mixing of dye with blood was confirmed in 1 sheep with 2 portal vein catheters. Surgery to place the catheters was facilitated by using a ventral para-costal approach. Blood gas analysis was useful in confirming the placement of the catheters. Useful catheter life in this experiment was 41 days, which was longer than in previous reports. Treating the catheters with an organo-silane preparation, protecting the catheters against dislodgement, and use of a belly bandage to minimize damage to the external parts of the catheter may have prolonged catheter life in this experiment.

Animals↗
PubMed1984

Hepatic and extrahepatic lactate metabolism in sheep: effects of lactate loading and pH.

Hepatic lactate metabolism was studied in five sheep receiving infusions of either lactic acid or sodium lactate using an arteriovenous difference technique. Hepatic uptake of lactate was a saturable process with second order (Michaelis-Menten) kinetics. Although lactic acid infusion decreased blood pH, hepatic saturation of lactate uptake occurred before changes in pH could influence hepatic lactate metabolism. The Vmax for hepatic lactate metabolism is 5.72 mmol X kg-0.75 X h-1 and the Km 3.06 mmol/l. These findings have therapeutic relevance. In acidosis, the hepatic response to therapeutic administration of sodium lactate during fluid therapy will be variable. If plasma lactate is low, lactated fluids may increase hepatic uptake and produce an alkalizing effect. If plasma lactate is already high, hepatic lactate metabolism is nearly saturated, and additional lactate will not produce a hepatic alkalizing response. Extrahepatic tissues switch from lactate production to lactate utilization under conditions of lactate loading. They remove more lactate than liver at high plasma lactate concentrations. Muscle may be important in lactate removal in certain types of exercise.

Animals↗
PubMed1984

Comparison of resting capillary flow dynamics in the finger and toe nailfolds.

The purpose of this study was to compare capillary dynamics in the nailfold regions of the human toes and fingers. Capillary blood flow velocity (VEL), vessel diameter, the total number of capillaries and the number of capillaries with active flow per mm2 of tissue were measured in the toe nailfold region of 17 and in the finger nailfolds of 15 male subjects 20 to 40 years of age. All measurements were made in the rest state at a skin temperature of 32 degrees C. Group averages were: (Formula: see text). These results demonstrate that compared to the finger the nailfold capillaries in the toe have a lower blood flow per vessel but a much higher capillary density. The combination of these factors indicates that total capillary blood flow is higher in the toe nailfold system.

Adult↗