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Biomedical subjects

R E Jones

Publications and source records attributed to R E Jones.

At least 145 records · Page 8Linked to original sources
PubMed1987

Microlesion formation in myocardial cells by high-intensity electric field stimulation.

Arrhythmias, S-T segment changes, immediate refibrillation, and other signs of dysfunction are often observed after clinical and experimental transthoracic defibrillation. In vitro studies suggested that shock-induced dysfunction is induced by sarcolemmal dielectric breakdown accompanied by ionic exchanges through transient, shock-induced microlesions in the sarcolemma. To test this hypothesis, cultured chick embryo myocardial cells were shocked in media containing fluorescein isothiocyanate-labeled dextrans (FITC-dextrans) ranging in molecular mass from 4 to 70 kDa, using electric field stimulation 5 ms in duration and ranging in intensity from 0 to 200 V/cm. Results showed that the percentage of cells incorporating 4- to 20-kDa dextrans increased in a dose-dependent manner. The 4- and 10-kDa dextrans were incorporated beginning at intensities of 50-100 V/cm. Dextran incorporation corresponded with shock intensities which produced a shock-induced arrest of spontaneous contraction lasting 1 min. The 20-kDa dextrans were incorporated following 150- and 200-V/cm shocks. Shocks of these intensities also produced a transient postshock contracture. Larger dextrans (40 and 70 kDa) were not incorporated. These results suggest the formation of transient sarcolemmal microlesions having a diameter of 45-60 A during high-intensity electric field stimulation.

Animals↗
PubMed1987

Improved cardiac cell excitation with symmetrical biphasic defibrillator waveforms.

According to the most commonly accepted hypothesis, ventricular defibrillation is produced by exciting cells in a critical mass of the ventricle. For monophasic defibrillator waveforms, this hypothesis correctly predicts a direct correlation between defibrillation threshold in the transthoracic calf model and excitation threshold for extracellular field stimulation in the cultured cell model. To further test the hypothesis, we determined whether symmetrical biphasic waveforms, which reduce defibrillation threshold in the calf to approximately 65% of that of the corresponding monophasic waveform (14), decrease excitation threshold in the cultured cell model. Experiments were performed on 100- to 250-microns aggregates from 10- to 12-day-old chick embryos. Excitation threshold strength-duration curves obtained at extracellular potassium (Ko) = 6.5 mM and pacing interval of 1,000 ms showed a significant reduction for symmetrical biphasic rectangular waveforms, when compared with the corresponding monophasic waveforms for durations greater than 3 ms. At the rheobase, the threshold ratio between the biphasic and monophasic waveforms was 0.63 (SE = 0.02). Transmembrane potentials during stimulation showed that excitation takes place during the second portion of the biphasic waveform for intensities that are subthreshold for the monophasic waveform. The relative effectiveness of the biphasic waveform (5-ms duration) increases under "fibrillation conditions" of short pacing interval (300 ms) and high extracellular potassium (10.5 mM). These results show that symmetrical biphasic waveforms decrease excitation threshold in the cultured cell model and that the degree of threshold reduction is dependent on Ko and beat rate.

Animals↗
PubMed1987

Accessory cell function of the endothelial cell: its role in the cellular immune response.

We have proposed a hypothesis in which vascular endothelial cells, rather than or in addition to bone-marrow-derived cells, play an integral part in the antigen presentation event of cell-mediated immune phenomena including delayed-type hypersensitivity (DTH). Previously we have shown that a DTH ear-swelling response can be adoptively transferred in rats, using as few as 2 x 10(7) in vitro conditioned immune spleen cells. The transfer is antigen-specific, requiring the same sensitizing antigen in both the in vitro conditioning step and in the ear-test challenge. Adoptive transfer is also genetically restricted by alleles of the RT-1 region of the rat, requiring histocompatibility between immune donor cells and the naive recipient. In additional experiments, F1 to parental bone-marrow chimaeras were constructed such that the bone-marrow-derived cells and the non-bone-marrow-derived cells were of different RT-1 allotypes. When these chimaeras were used as adoptive transfer recipients, the transfer of DTH was possible only if the immune donor cells and the recipient non-bone-marrow-derived cells shared a common RT-1 haplotype, regardless of a shared haplotype with the bone-marrow-derived cells. These results point to a critical role for non-bone-marrow-derived cells (endothelial cells) in the DTH inflammatory response.

Animals↗
PubMed1986

Tracheal reconstruction with autogenous jejunal microsurgical transfer.

Tracheal defects due to stricture formation, tracheomalacia, and neoplasms can present difficult reconstructive problems. Tracheal defects were surgically created in 6 dogs and primarily reconstructed with microsurgical free tissue transfer of autogenous jejunal segments. Primary healing was accomplished in all dogs without severe air leakage or infection. Bronchoscopy demonstrated no substantial secretions or tracheal narrowing. Gross pathological examination of the trachea revealed no evidence of tracheal disruption or infection. Direct measurements revealed no major tracheal narrowing. Microscopic examination demonstrated normal jejunal mucosa with a minimal amount of inflammatory change at the margins of the reconstruction at 6 weeks. Microvascular free tissue transfer of jejunal segments to correct cervical tracheal defects can readily be accomplished with excellent healing and maintenance of the tracheal lumen in dogs.

Animals↗
PubMed1986

Thyrotoxicosis associated with distant metastatic follicular carcinoma of the thyroid.

In a man with metastatic follicular carcinoma of the thyroid, thyrotoxicosis developed after total thyroidectomy and was successfully treated with antithyroid medications. Treatment with radioactive iodine decreased the size of the distant metastasis and eventually diminished thyroid hormone production. Follicular carcinoma complicated by hyperthyroidism requires vigorous control of the hypermetabolic state. Treatment with radioactive iodine can effectively reduce metabolic complications and tumor bulk, and yields a remission rate as high as 33%.

Adenocarcinoma↗
PubMed1986

Light-induced interaction between rhodopsin and GTP-binding protein leads to the hydrolysis of GTP in the rod outer segment.

In the presence of exogenous GTP, vertebrate whole rod outer segments (ROS), with perforated plasma membranes in the "single particle" scattering range, elicit a light-induced light-scattering transient which we call the "G" signal. Here, we report on the characteristics of the "G" signal relative to the "binding" and "dissociation" signals reported by Kuhn and colleagues. Replacing GTP with guanylyl imidodiphosphate (GMP-PNP) does not give rise to the G signal. This indicates that hydrolysis of the terminal phosphate is required for the G signal and, in addition, GTP and GMP-PNP compete for the same binding site of the enzyme responsible for the G signal (i.e., GTP-binding protein). Also, neither GDP nor its nonhydrolyzable analogue, guanosine 5'-O-(2-thiodiphosphate), when present in ROS suspensions yield any light-scattering transient in the time period tested.

Animals↗
PubMed1986

Prophylaxis with cefamandole nafate in elective orthopedic surgery.

A prospective, randomized, double-blind study was conducted to determine the efficacy of cefamandole nafate in reducing infections in general orthopedic procedures. Of 743 patients initially entered into the study, 715 (362 on cefamandole, 353 on placebo) fulfilled the requirements of the protocol. The infection rate was 1.6% for the cefamandole-treated group and 4.2% for the placebo group. In operations lasting longer than two hours, there were two infections in the cefamandole group and seven infections in the placebo group (p less than 0.05). Staphylococcus aureus and gram-negative bacilli were the common pathogens. Adverse side effects were limited to transient elevations in liver enzymes.

Adult↗
PubMed1986

Nonoperative management of isolated grade III collateral ligament injury in high school football players.

In a prospective study, 24 high school football players with isolated Grade III injuries of the medial collateral ligament (MCL) of the knee were treated by conservative management. This included an active rehabilitation program, progressing from immobilization and controlled motion in an orthotic rehabilitation knee brace, to muscle strengthening and agility exercise. A stable knee was achieved in 22 cases; the average recovery time was 29 days. The athletes returned to competitive sports at a mean time of 34 days. These results confirm previous reports of successful nonoperative management of isolated Grade III MCL injuries.

Adolescent↗
PubMed1985

Multiple sclerosis: abnormalities in luminance, chromatic, and temporal function at multiple retinal sites.

Visual function was assessed in a group of patients with multiple sclerosis (MS) and in a group of matched normal controls. In these patients the disease was relatively mild. For each subject, measures of a range of psychophysical visual functions were carried out at multiple sites in each eye. Previous reports have only included some of these functions. Here, luminance threshold, two-flash resolution, perceptual latency, luminance critical flicker frequency (CFF), and chromatic CFF were all measured. Variabilities of these functions and correlation between chromatic and luminance CFFs were also evaluated. For both the MS group and the normal control group, the correlations between pairs of visual parameters were not overall significantly greater than chance level. The MS group did give a significantly reduced value relative to the normal group for luminance CFF and for the gradient of the plot of chromatic CFF against luminance CFF. This group was then subdivided according to history of visual involvement. The subgroup with previous visual symptoms had significant impairment for luminance threshold, variability of luminance threshold, luminance CFF, variability of two-flash resolution, and for the gradient of the plot of chromatic CFF against luminance CFF. The subgroup without previous visual symptoms showed no significant impairment for any individual parameter, although the gradient of the plot of chromatic CFF against luminance CFF was lower than normal.

Adult↗
PubMed1985

Induction of oviposition in cycling Anolis carolinensis requires a beta-adrenoreceptor blocker and a high dosage of arginine vasotocin.

In a previous study, a high dosage (2.0 micrograms) of arginine vasotocin (AVT), following 10 micrograms of dichloroisoproterenol, induced oviposition in Anolis carolinensis at the end of the breeding season. The present study determined if a lower dosage of AVT (0.25 microgram), comparable to that effective in other lizard species, would induce oviposition in cycling A. carolinensis. Only a high dosage of AVT (2.0 micrograms), following 10 micrograms of dichloroisoproterenol 15 min beforehand, induced oviposition. These results suggest that uterine smooth muscle of A. carolinensis is relatively insensitive to AVT.

Adrenergic beta-Antagonists↗
PubMed1985

Sham feeding, flavor associations and diet self-selection as indicators of feeding satiety or aversive effects of peptide hormones.

We have attempted to develop a constellation of behaviors which show differential effects following the administration of putative satiety hormones (CCK-8, BBS, insulin) as opposed to effects seen following a toxin, such as LiCl. In the initial behavior assessed, sham feeding of differently paired, flavored milks (flavor paired with insulin, BBS or saline) was carried out. Male adult Sprague-Dawley rats which sham fed milk flavors paired with 16 micrograms/kg BBS showed a significant aversion of that flavor in a two-bottle taste test (compared to saline-paired flavors, p less than 0.001) but a significant preference for flavored milk paired with 0.4 and 0.75 U insulin/rat. Lower dosages of BBS (4 and 8 micrograms/kg) and insulin (0.1 U/rat) showed no significant aversion or preference when compared to saline. The second behavioral paradigm evaluated the effects of the hormones CCK-8 and BBS and the toxin, LiCl, upon self-selection of pure macronutrients. While CCK-8 reduced intake of calories by significantly lowering ingestion/selection of fats (55%, p less than 0.01 compared to saline, control injections) and carbohydrates (50%, p less than 0.01), LiCl and BBS reduced calories by decreasing selection of primarily proteins (LiCl--49%, p less than 0.03; BBS--63% at 4 micrograms/kg and 80% at 8 micrograms/kg, both p less than 0.025). In both paradigms then, BBS at doses sufficient to significantly reduce sham intake or suppress caloric ingestion in a self-selection paradigm produced behavioral effects most similar to those observed following the injection of a toxin. LiCl, rather than effects seen following other various putative satiety signals.

Animals↗