PubMed Health⌕ Search

Biomedical subjects

D K Gardner

Publications and source records attributed to D K Gardner.

88 records · Page 5Linked to original sources
PubMed1992

Surfactant replacement therapy: development of criteria for appropriate use. Ohio State University Hospitals.

At The Ohio State University (OSU) Hospitals, DUE criteria were established when colfosceril palmitate, a synthetic surfactant, was added to the formulary in January 1991. The DUE criteria were designed to assure appropriate drug use, educate physicians, and establish an effective way to monitor drug use and patient outcome (ie, response rate and complications). The criteria include a mechanism for evaluation and modification of the guidelines, as necessary. In addition, a review process will be used to determine the therapy's cost effectiveness and to serve as a guideline for making recommendations on other surfactant formulations as they become available.

Cost-Benefit Analysis↗
PubMed1991

Analgesia versus sedation during Broviac catheter placement.

Premature infants are capable of mounting physiologic and metabolic responses to pain. Systemic and local anesthesia reduce stress responses to major and minor surgical procedures. We evaluated the effects of local anesthesia (5 mg/kg lidocaine) preceded by either 1 mg/kg secobarbital (S) intravenously or by 2 micrograms/kg fentanyl (F) intravenously on the stress response to Broviac catheter placement. Twenty-nine premature infants ages 5 to 30 days, weighing between 650 and 1350 gm, were randomly assigned to either S or F groups. Age, birthweight, sex, race, and severity of illness were similar among S and F groups. Heart rate and blood pressure remained unchanged throughout the procedure. Oxygen saturation (O2sat) declined significantly in both groups during skin preparation and wound closure, but not during incision, dissection, or tunneling. In spite of fractional inspired oxygen adjustments made in 13 of 14 S- and 3 of 15 F-treated patients, decline in O2sat was more common and more pronounced (p less than 0.01) in S-treated babies. Hyperglycemic responses occurred in all S- and in none of the F-treated patients (p less than 0.001). Norepinephrine plasma concentrations did not change during Broviac catheter placement in either F or S group. Epinephrine concentrations were more elevated in S- than in F-treated patients, although these differences were not statistically significant. Low-dose fentanyl analgesia effectively complements local lidocaine anesthesia during Broviac catheter placement. Sedatives neither abolish metabolic responses to surgical stress nor prevent profound and persistent oxygen desaturation.

Blood Glucose↗
PubMed1991

Oxygen concentration and protein source affect the development of preimplantation goat embryos in vitro.

The effect of oxygen concentration and the source of protein in culture medium on the development of 2- to 4-cell goat embryos in vitro was investigated. Embryos were collected from superovulated Angora-Cashmere-cross goats 48 h after ovulation and cultured for 6 days in synthetic oviduct fluid (SOF) medium under one of two oxygen concentrations (20% or 7%) and in the presence of one of five protein sources; Miles bovine serum albumin (Miles BSA), Commonwealth Serum Laboratory bovine serum albumin (CSL BSA), goat serum (GS), fetal calf serum (FCS) and human serum (HS). In the presence of 20% oxygen the percentage of embryos reaching the expanded and/or hatched blastocyst stage in SOF medium containing Miles BSA was 29%, with a mean cell number per embryo of 28.1 +/- 6.0 (+/- s.e.m.). Use of an oxygen concentration of 7% significantly increased the percentage of embryos reaching this stage (80%, P less than 0.01) and the mean number of cells per embryo (65.3 +/- 8.2, P less than 0.01). The mean number of cells of the early-cleavage-stage embryos was significantly lower when the medium contained CSL BSA, GS or FCS (42.7 +/- 5.6, 29.0 +/- 6.1 and 21.3 +/- 3.2, respectively) than with Miles BSA (92.8 +/- 6.4) or HS (104.8 +/- 17.2) (P less than 0.01). Under 7% oxygen and with Miles BSA or HS, embryos were morphologically comparable to those developed in vivo, but the mean cell numbers in vitro were only approximately half those obtained in vivo.

Animals↗
PubMed1990

Concentrations of nutrients in mouse oviduct fluid and their effects on embryo development and metabolism in vitro.

An ultramicrofluorometric technique was used to analyse the nutrient composition of mouse oviduct fluid. The concentrations of pyruvate, glucose and lactate in the vicinity of the cumulus mass were 0.37, 3.40 and 4.79 mM respectively. In the absence of cumulus cells, the concentration of pyruvate was significantly reduced, to 0.14 mM, while the concentration of glucose was significantly increased to 5.19 mM. Glutamine, which may help to overcome the '2-cell block' in mouse embryos in culture, was present at a concentration of 0.20 mM. A modified medium (MTF) in which the concentration of nutrients was similar to that in mouse oviduct fluid was prepared and its effects on embryo development and metabolism in vitro were compared with that of a conventional embryo culture medium (M16). The percentage of zygotes forming blastocysts in vitro by Day 5 was similar in both media (82% in M16, 79% in MTF). Rates of development, as assessed by cell number, were also comparable. However, the proportion of glucose consumed which was converted to lactate increased dramatically following culture; from 44% in fresh blastocysts, to 73% and 91% in blastocysts derived from 8-cell embryos cultured for 24 h in media MTF and M16 respectively.

Animals↗
PubMed1989

Development of a noninvasive ultramicrofluorometric method for measuring net uptake of glutamine by single preimplantation mouse embryos.

A noninvasive ultramicrofluorometric method for measuring net uptake of glutamine by single preimplantation mouse embryos is described. A linear relationship was found between fluorescence intensity of NADH produced and glutamine concentration (R2 = 0.985). Single embryos were placed in 20 nl drops of medium containing 0.5 mM glutamine, and the medium was sampled after 2 hr incubation at 37 degrees C. Changes in net glutamine uptake were determined in one-cell, two-cell, and eight-cell embryos and blastocysts incubated in medium containing no energy substrates (glucose, pyruvate, and lactate). The median glutamine uptake increased significantly from 0.480 and 0.270 pmoles/embryo/2 hr at the one-cell and two-cell stages, respectively, to 1.610 pmoles/embryo/2 hr at the blastocyst stage. Mean glutamine uptake was compared in the presence or absence of energy substrates at several developmental stages. A highly significant reduction of glutamine uptake in the presence of substrates was observed at the one-cell and two-cell stages of development. At the eight-cell stage, glutamine uptake was only marginally reduced in the presence of substrates, and no effect was found at the blastocyst stage. These data may partially explain the beneficial effect of glutamine on the culture of early mouse embryos through the two-cell block of development.

Animals↗
PubMed1988

The role of glucose and pyruvate transport in regulating nutrient utilization by preimplantation mouse embryos.

Preimplantation mouse embryos utilize pyruvate preferentially during the early cleavage stages before switching to glucose at around the time of compaction. This switch in substrate preference has been studied using a non-invasive ultramicrofluorometric analytical technique on single mouse embryos. On the basis of transport kinetic studies and inhibition by phloretin, cytochalasin B and sugar analogues, a component of glucose uptake by mouse blastocysts was found to be mediated by facilitated diffusion. The Jmax and Kt of this facilitated component were 3.53 pmol embryo-1 h-1 and 0.14 mM, respectively. At physiological concentrations of glucose, the facilitated component accounts for around 75% of glucose uptake. Glucose uptake by blastocysts was found to be insensitive to insulin, added at a range of concentrations. There was no evidence for glucose active transport. The carrier-mediated component of glucose entry was detectable from the 2-cell stage onwards. Pyruvate uptake was also mediated by a carrier throughout development. In the absence of glucose in the incubation medium, the characteristic decline in pyruvate uptake does not occur. The data are consistent with a role for embryonic cell transport in regulating glucose utilization prior to compaction, but do not exclude the involvement of metabolic factors, such as the allosteric regulation of the enzymes hexokinase and phosphofructokinase.

Animals↗
PubMed1987

Assessment of embryo viability prior to transfer by the noninvasive measurement of glucose uptake.

An ultramicrofluorometric technique was used to measure the uptake of glucose by single mouse blastocysts prior to transferring them into the uterus of pseudopregnant foster mothers. Of 50 blastocysts whose glucose uptake was measured prior to embryo transfer, 25 gave rise to male and 13 to female offspring. Twelve embryos failed to develop. The mean glucose uptake of these 12 embryos was significantly below that of those which developed successfully. Female embryos took up slightly more glucose than male embryos.

Animals↗
PubMed1986

Non-invasive measurement of nutrient uptake by single cultured pre-implantation mouse embryos.

The uptake of pyruvate and glucose by single, cultured mouse embryos has been measured non-invasively throughout the pre-implantation period. The embryos, derived from CBA x C57F1 females and F1 males were removed from the oviducts on day 1 or day 2 following mating, and cultured to the blastocyst stage in M16 medium. Each day they were removed from culture and incubated in 20 nl medium M2 for 3 h. Serial approximately 0.5-nl samples were analysed for pyruvate and glucose by an ultramicrofluorescence technique. Pyruvate uptake exceeded that of glucose until the 8-cell/morula stage, when glucose consumption increased dramatically. The morphological development and patterns of nutrient uptake by embryos removed on day 2 resembled more closely those of freshly collected embryos than of embryos removed on day 1. These methods will enable the biochemistry of early embryos to be monitored non-invasively prior to transferring them into the uterus of recipient females.

Animals↗
PubMedDate not supplied

Concentrations of energy substrates in oviduct fluid in unilaterally ovariectomised pigs.

Nichol et al (1992, Journal of Reproduction and Fertility, 96, 699-707) identified a pre- to post-ovulatory decrease (approx 1 mM) in the amount of glucose in pig oviduct fluid. The present studies investigated whether the decrease was due to metabolism by embryos and/or oviduct tissues, and also whether there was a local influence of the ovary on the oviduct fluid content of energy substrates. Unilaterally ovariectomised pigs were used, in which, through compensation, oviducts that contained twice the normal number of embryos could be compared with oviducts which contained no embryos. Following unilateral ovariectomy and after two oestrous cycles of normal duration, surgery was performed 88 hours after the beginning of standing heat to obtain oviduct fluid samples, just before embryonic entry into the uterus. Luminal fluid samples from the ampulla and ampullary-isthmic junction from oviducts with and without an adjacent ovary were assayed for glucose, pyruvate and lactate concentrations. No significant differences were found between the glucose, pyruvate and lactate concentrations in fluids from the ampulla or ampullary-isthmic junction from oviducts containing embryos compared with absence of embryos (P > 0.05). Therefore, the post-ovulatory decrease was not due to the presence of embryos or to a local effect of the ipsilateral ovary. Consequently, pig oviduct fluid concentrations of glucose, lactate and pyruvate are seemingly regulated by systemic mechanisms.

Animals↗
PubMedDate not supplied

Culture and selection of viable blastocysts: a feasible proposition for human IVF?

In human in-vitro fertilization (IVF) embryos are routinely transferred to the uterus on day 2 or day 3 of development. Resultant implantation and pregnancy rates are disappointingly low, with only approximately 10% of embryos transferred leading to a live birth. The ability to culture embryos to the blastocyst stage should help to resolve this problem by synchronizing the embryo with the female reproductive tract, and by identifying those embryos with little developmental potential. Co-culture has offered a possible means of producing blastocysts capable of high implantation rates. However, recent developments in the field of embryo physiology and metabolism have led to the formulation of new sequential serum-free culture media capable of supporting the development of viable blastocysts in several mammalian species, including the human. It is therefore proposed that blastocyst transfer should be considered for routine use in human IVF. The high viability of blastocysts cultured in the appropriate sequential media means that fewer embryos are required for transfer to achieve a pregnancy, culminating in fewer multiple births. Furthermore, the development of suitable non-invasive tests of embryo viability should further increase the overall success of human IVF by the ability to select before transfer those blastocysts most able to establish a pregnancy.

Amino Acids↗