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Biomedical subjects

M L Baker

Publications and source records attributed to M L Baker.

At least 19 recordsLinked to original sources
PubMed1992

The acceleration of gallstone destruction with synchronous biliary lithotripsy and contact dissolution in vitro using three cholesterol-solubilizing solvent.

In the first-known application of its kind, shockwave lithotripsy and contact-solvent dissolution of large, calcified gallstone burdens were performed simultaneously with three chemical solvents, each tested separately in an in vitro model, with the combined effects on gallstone eradication examined. Two solvents, ethyl propionate and isopropyl acetate, were chosen for their solubilizing ability and potentially high level of patient safety. The third solvent, a 70%:30% mixture of methyl tert-butyl ether (MTBE) and dimethyl sulfoxide (DMSO), was chosen for its known ability to accelerate the dissolution of calcium-containing gallstones. All stones were matched for size, weight, and number. Gallstone lithotripsy performed in ethyl propionate was significantly more effective (P less than .02) in the production of fragments less than 2 mm when compared with bile; lithotripsy with isopropyl acetate and the MTBE/DMSO mixture showed no statistically significant effect. Biliary lithotripsy performed in an ethyl propionate medium may enhance gallstone dissolution and the production of small fragments (diameter less than 2 mm).

Acetates↗
PubMed1991

The effect of ionizing radiation on the viability of Trichomonas vaginalis.

1. The effects of continuous gamma radiation on the viability of Trichomonas vaginalis (ATCC 30001) were assessed by a colony count technique. 2. A triphasic survival curve showed an initial shoulder (Dq) of 3 Gy followed by three linear curves with D0 values of 34, 300, and 90 Gy. 3. Sterilization of 10(6) cells/ml occurred from 1600 to 1800 Gy of radiation. 4. Population growth, subsequent to radiation exposure of 17-100 Gy, showed an increased lag time followed by a faster rate of growth, compared with unirradiated cells. 5. Trichomonas vaginalis is more sensitive to ionizing radiation than free-living protozoa and appears as radiosensitive as those parasitic protozoa examined in radioattenuation experiments.

Animals↗
PubMed1991

Axis fracture in ankylosing spondylitis: case report.

Ankylosing spondylitis is a chronic inflammatory disease that results in the slow progressive transformation of the normal spine into a rigid and brittle tube containing the normal neural elements. This pathological condition predisposes the patient to fractures of this structure and a potential for neurological damage greater than that of the normal population. We present a spontaneous fracture of the C1-C2 complex through the base of the dens, with impending neurological deficits in such a patient. We have reviewed the pertinent literature and emphasized several points relative to the management of similar patients.

Axis, Cervical Vertebra↗
PubMed1991

In vitro cholesterol gallstone dissolution: comparison of methyl tert-butyl ether with three new ester solvents.

The in vitro effectiveness of three new cholesterol gallstone solvents that have a potential for clinical use--ethyl propionate, isopropyl acetate, and n-propyl acetate--was compared with that of the well-known cholesterol solvent methyl tert-butyl ether (MTBE). Ten sets of matched gallstones were initially weighed, imaged with radiography and computed tomography (CT), and analyzed for content. One stone from each set was incubated in one of the four solvents at 37 degrees C. Solvents were changed at 30-minute intervals. The study was stopped either when the stones were completely dissolved or at the end of 7 hours. Any residual fragments were weighed, reimaged, and reanalyzed for content. There were no statistical differences between dissolution times of the stones in MTBE compared with those in the three new solvents. Ethyl propionate and n-propyl acetate appear to be as efficacious as MTBE in dissolving cholesterol stones and could be attractive alternatives for gallstone chemolysis.

Acetates↗
PubMed1990

Modulation of memory processing by glutamic acid receptor agonists and antagonists.

Recent hypotheses suggesting a critical role of glutamate receptors in hippocampal long-term potentiation and memory processing suggested a closer examination of this transmitter's effect on memory processing in an in vivo setting. New pharmacological antagonists allow for a separation and examination of various glutamate receptors and their role in memory processing. Mice were trained on a shock avoidance learning paradigm and injected intracerebroventricularly after training with agonists and antagonists of various classes of glutamate receptors. Retention was tested 1 week after training. N-Methyl-D-aspartate (NMDA) receptor agonists enhanced retention in a dose-dependent manner. The enhancement of retention by the non-NMDA agonist kainic acid and quisqualic acid was dose-dependent. L-Glutamic acid, but not D-glutamic acid, enhanced retention. Both NMDA and non-NMDA receptor antagonists produced dose-dependent impairment of retention for footshock training. Administration of the antagonists 24 h after training did not impair memory retention.

Animals↗
PubMed1990

Modulation of memory retention by neuropeptide K.

Neuropeptide K (NPK) is one of the structures in beta-preprotachykinin which also includes substance P. NPK, a 36 amino acid peptide, contains the sequence of neurokinin A as amino acids 27-36 of its C-terminus. Neurokinin A is also contained separately in the gamma-preprotachykinin precursor. Both NPK (2.5-10 micrograms) and neurokinin A administered intracerebroventricularly after footshock avoidance training in the T-maze enhanced memory retention in CD-1 male mice. Local microinjections of NPK enhanced memory retention when injected into the rostral and caudal portions of the hippocampus (0.25 and 0.50 microgram) and the amygdala (1.0 microgram), but were without effect when injected into the septum and the caudate. The differential effects of NPK on memory retention across brain regions differed from those previously reported for substance P and neuropeptide Y. These studies suggest that NPK, acting through discrete anatomical areas, modulates memory processing. The functional significance of co-localization of neuropeptides with classical neurotransmitters and other transmitter peptides in the same neurons is not well understood, but recent studies have indicated that the neuropeptides modulate the release of the primary transmitter. Since NPK occurs in the same precursor molecule as substance P, NPK may be co-released with the putative neurotransmitter substance P and act with it, in a synergistic manner, to enhance memory processing. These studies provide further evidence that the hippocampus is an anatomical structure involved in memory processing that occurs shortly after training.

Amino Acid Sequence↗
PubMed1990

Pentobarbital tolerance and withdrawal: correlation with effects on the GABAA receptor.

A model for the development of pentobarbital tolerance and dependence was characterized and correlated with changes in radioligand binding to the GABAA-benzodiazepine receptor chloride channel complex. While one day of pentobarbital exposure decreased the duration of loss of righting reflex, tolerance to the hypothermic effects of thiopental and barbital took 7 days to develop, indicating that pharmacokinetic and pharmacodynamic tolerance are separable. Increased sensitivity to pentylenetetrazol-induced seizures was first observed after 3 days of pentobarbital exposure, suggesting brain areas involved in seizure control develop tolerance to, and dependence on pentobarbital faster than those involved in temperature regulation. Acute exposure to pentobarbital in vivo did not affect cortical binding of [3H]muscimol in vitro, while tolerance caused a decrease in binding due to an increase in the low-affinity site KD. Pentobarbital tolerance also caused a decrease in the cortical binding of the benzodiazepine, [3H]flunitrazepam. These observations suggest that the acute effects of barbiturates on the GABAA receptor complex are reversible, while tolerance causes receptor modifications which may be related to the development of physical dependence.

Animals↗
PubMed1990

Serum levels of müllerian inhibiting substance in boys from birth to 18 years, as determined by enzyme immunoassay.

An enzyme immunoassay was set up with the aim of determining the serum levels of Müllerian inhibiting substance (MIS) during childhood. A monoclonal antibody against purified bovine MIS was combined with a polyclonal antibody against recombinant human MIS to make a sandwich assay. This assay detected MIS in human serum within the following criteria. Ninety-eight boys, aged between birth and 18 yr, who had been admitted to the Royal Children's Hospital, were included. MIS levels were measured in samples taken for biochemical screening of unrelated disorders. MIS was detected in the serum up to 16 yr of age, but was low beyond 12 yr and undetectable at 18 yr. High MIS levels were found at 4-12 months, consistent with MIS having an important function at this time. Germ cells undergo an important transformation from gonocytes to spermatogonia at the same time as the MIS levels peak, suggesting a possible function for MIS.

Adolescent↗
PubMed1990

Amplatz vena caval filter: clinical experience in 30 patients.

Amplatz vena caval filters were inserted percutaneously in 30 patients. Radiologic and clinical follow-up was available in 24 patients (cavogram, CT, or sonography in 20 patients, plain abdominal radiographs in two, and lower extremity venograms in two). Clinical follow-up only was available in four patients, and autopsy reports were available in two patients without radiologic follow-up. The filter was inserted without difficulty in 29 (97%) of the patients. Complications after insertion included recurrent pulmonary embolism in two (7%) of 30, caval thrombosis in seven (23%) of 30, ipsilateral lower extremity deep venous thrombosis after placement of the filter in one (3%) of 30, caval penetration in two (10%) of 20, and caval stenosis in one (5%) of 20. No migration of the filter was noted. Our experience suggests that the Amplatz vena caval filter is easy to insert and adequately prevents recurrent pulmonary embolism but is associated with a relatively high rate of caval thrombosis.

Aged↗
PubMed1990

Postirradiation treatment with copper(II)2(3,5-diisopropylsalicylate)4 enhances radiation recovery and hemopoietic regeneration.

We have previously reported that copper(II)2(3,5-diisopropylsalicylate)4 (Cu-DIPS), administered 3 h before exposure to lethal irradiation, significantly increased the survival rate of mice. Agents that can improve recovery from irradiation are of particular importance for accidental radiation exposure if they are effective when given after exposure. In the present study, we showed that Cu-DIPS had radiation recovery activity when administered subsequent to radiation exposure. Mice were exposed to 800 cGy irradiation and 3 h later injected with vehicle or 20, 40, or 60 mumol/kg Cu-DIPS. The 30-day survival rate was significantly increased at all doses of Cu-DIPS tested. Survival increased from 47% for vehicle-treated mice to 78% (p less than 0.001) for mice treated with 40 mumol/kg. The recovery of hemopoietic activity was assessed in similarly treated mice 14 and 24 days after irradiation. The postirradiation Cu-DIPS treatment significantly increased spleen weights, bone marrow cellularity, and hemopoietic activity in the spleen and bone marrow compared to vehicle-treated controls. Enhanced recovery of hemopoietic activity included both committed progenitor granulocyte-macrophage colony-forming units (GM-CFU) and more primitive stem cells (endogenous spleen colony-forming units, CFU-Se). The number of CFU-Se at 14 days, the number of bone marrow GM-CFU at 24 days, and bone marrow cellularity at 24 days appear to be better predictors of survival rates than other parameters.

Animals↗
PubMed1989

Modulation of memory processing by neuropeptide Y varies with brain injection site.

Neuropeptide Y (NPY) is a 36 amino acid peptide which was shown to enhance memory retention, recall and prevent amnesia induced by either scopolamine or anisomycin. In this study, we examined the effects of NPY administration into 6 areas of the mouse brain on memory retention for footshock avoidance training in a T-maze. NPY was injected into the rostral and caudal hippocampus, amygdala, caudate, septum and thalamus shortly after training. NPY improved retention when injected into the rostral portion of the hippocampus and septum, impaired retention in the caudal portion of the hippocampus and amygdala and had no effect in the thalamus and caudate. NPY was ineffective at either improving or impairing retention when injected 24 h after training, thus demonstrating that the effects of NPY on retention were time-dependent and not due to proactive effects on retention test performance per se. In addition, NPY had no effect on retention when injected into overlying cortical areas. NPY antibody impaired retention when administered into the rostral hippocampus and septum; it improved retention in the caudal hippocampus and amygdala. Thus NPY antibody had the opposite effect to that of NPY on memory retention suggesting that NPY has a physiological role as a modulator of memory processing within specific anatomical areas of the central nervous system.

Animals↗
PubMed1989

Bioavailable copper complexes offer a physiologic approach to treatment of chronic diseases.

Copper (II)2(3,5-Diisopropylsalicylate)4(H2O)2 has been found to have antiinflammatory, antiulcer, anticonvulsant, anticancer, anticarcinogenic, antimutagenic, and radiation recovery activities and it prevents reperfusion injury. To study pharmacokinetic parameters accounting for these pharmacological effects the double labeled 67Cu(II)2(carboxy-14C-3,5-diisopropylsalicylate)4 complex was synthesized and used to obtain these parameters. Treatment of mice with 1 mumol of this complex revealed that 67Cu was distributed to blood, liver, kidney, intestine, lung, thymus, femur, muscle, spleen, brain, urine, and feces within 0.5 hr and patterned changes in 67Cu content of these tissues and excreta were found throughout the 96 hr term of this study.

Animals↗
PubMed1988

Laser thermal angioplasty for the treatment of obstruction of the distal superficial femoral or popliteal arteries.

The success rates and clinical effectiveness of percutaneous laser thermal angioplasty for obstruction of the distal superficial femoral or popliteal arteries were assessed. Laser thermal angioplasty was performed with the first commercially available laser system on 25 atherosclerotic vascular lesions in 20 lower extremities of 18 patients. Fifteen of the lesions were occlusions (average length, 5.6 +/- 3.1 cm), and 10 were high-grade stenoses (average length, 2.6 +/- 1.8 cm). Indication for angioplasty was claudication limiting life-style in 12 extremities and threatened limb loss in eight. All patients were treated with a 1.5- or 2.0-mm metal-capped optical fiber attached to a 14-W argon-ion laser. Balloon angioplasty was performed after laser recanalization in all successful cases. The patients were followed by Doppler ankle/brachial index and clinical evaluation. Laser thermal angioplasty was technically successful (vessel recanalization) in 18 (90%) of 20 of the cases. Fourteen (70%) of 20 extremities were successes by ankle/brachial index follow-up, while 15 (75%) of 20 remained clinically improved after an average follow-up of 7.8 +/- 5.3 months. Laser thermal angioplasty has a technical and clinical success rate that compares favorably with previous reports of balloon angioplasty. With proper patient selection, laser thermal angioplasty can reduce the difficulty of traversing lesions that are amenable to standard balloon angioplasty and increase the number of vascular lesions that can be treated percutaneously but could not be recanalized without the use of laser energy.

Aged↗
PubMed1988

Copper(II)2(3,5-diisopropylsalicylate)4 stimulates hemopoiesis in normal and irradiated mice.

We have previously reported that copper(II)2(3,5-diisopropylsalicylate)4 (Cu-DIPS) significantly increased the survival rate of mice exposed to lethal irradiation. To examine whether Cu-DIPS affected hemopoietic activity, groups of mice were treated with Cu-DIPS or vehicle and assayed for in vitro interleukin 3 (IL-3)-dependent colony-forming units (CFU-C) and for committed progenitor granulocyte-macrophage CFU (GM-CFU). Cu-DIPS increased the number of splenic IL-3 CFU-C by five- to sixfold 7 days after treatment and splenic GM-CFU by 12-fold on day 24. These increases were accompanied by a 50% increase in spleen weight. Bone marrow IL-3 CFU-C and GM-CFU were not affected at 7 or 14 days after treatment, but were somewhat depressed at 24 days. In irradiated (8.0 Gy) mice treated with Cu-DIPS or vehicle, splenic IL-3 CFU-C and GM-CFU were undetectable 7 days after irradiation, but recovered more rapidly in Cu-DIPS-treated mice. By 24 days splenic IL-3 CFU-C in Cu-DIPS-treated mice recovered to 150% of normal (unirradiated) values and GM-CFU recovered to 270% of normal, whereas irradiated control values remained at 25% and 7%, respectively. The recovery of bone marrow hemopoiesis was slower than spleen, but 42 days after irradiation Cu-DIPS-treated mice had higher levels of bone marrow IL-3 CFU-C (eightfold) and GM-CFU (4.6-fold) than vehicle-treated mice. Cu-DIPS stimulated sixfold increases in renewable, pluripotent stem cells as measured by the in vivo assay of endogenous colony-forming units (CFU-Se).

Animals↗
PubMed1987

Copper(II)(3,5-diisopropylsalicylate)2 accelerates recovery of B and T cell reactivity following irradiation.

Copper(II)(3,5-diisopropylsalicylate)2 (Cu-DIPS), administered subcutaneously to mice at 80 mg/kg body weight, had marked radioprotective activity. Given 3 h before exposure to 8.0 Gy (800 rad) irradiation, Cu-DIPS increased the 42-day survival from 40% to 86%. Seven days after exposure to 8.0 Gy, there were severe reductions in spleen weight (73%) and cellularity (98%) in both Cu-DIPS- and vehicle-treated mice. Viable spleen cells collected 7 days after irradiation were totally unresponsive to mitogenic or antigenic stimulation regardless of Cu-DIPS or vehicle treatment, suggesting that Cu-DIPS did not prevent radiation-induced damage to mature lymphocytes. At 14 days, when Cu-DIPS-treated mice started to show improved survival over vehicle-treated mice, spleen weights and cellularity were 2.5- and 3.5-fold higher, respectively, in Cu-DIPS-treated mice. Treatment with Cu-DIPS not only enhanced splenic repopulation, but also accelerated the reappearance of both B and T cell reactivities. Spleen cell responsiveness to the B cell mitogen, lipopolysaccharide (LPS), and the T cell mitogen, concanavalin A (Con A), regenerated significantly faster in Cu-DIPS-treated mice. Cu-DIPS also significantly accelerated the regeneration of T-dependent antibody induction. Based on these assays of immunocompetence, Cu-DIPS-treated mice had, on average, a seven-fold greater capacity to respond to immune stimulation than vehicle-treated mice 24 days after irradiation.

Animals↗