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Biomedical subjects

J D Mann

Publications and source records attributed to J D Mann.

At least 37 records · Page 2Linked to original sources
PubMed1983

Saturable accumulation of the anionic herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), by rabbit choroid plexus: early developmental origin and interaction with salicylates.

Transport of the anionic herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D) was examined in vitro via the isolated choroid plexus of adult and neonatal rabbits and in vivo via ventriculocisternal perfusion. In vitro, the facilitated transport of 2,4-D by the choroid plexus was established in the rabbit by as early as 3 days of age. Uptake in both adults and neonates took place against a concentration gradient via a saturable process that was inhibited by ouabain and hypothermia (0 degrees C). Probenecid and hippuric acid were effective dose-dependent inhibitors of 2,4-D transport in vitro. The major metabolite of salicylate, salicyluric acid, was also an effective inhibitor, more than its precursor, salicylate, or gentisic acid, a second salicylate metabolite. Neither phenol, acetaminophen nor glycine inhibited 2,4-D transport. Thus, the effects appear specific for those compounds which share the organic acid transport system. The role of carrier-mediated transport in the clearance of 2,4-D from cerebrospinal fluid (CSF) was also evaluated in vivo by ventriculocisternal perfusion. Steady-state clearance of 2,4-D from CSF exceeded that of inulin and was reduced in a dose-dependent fashion in the presence of salicylate. Neither CSF formation nor absorption rates were changed. These results indicate that 2,4-D is transported from the CSF via the organic anion transport system, and that inhibitors of this transport system may block its elimination from the brain in vivo, just as they block its transport by the isolated choroid plexus.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1982

The effect of academic preparation on medical technologists' registry examination performance.

This study investigated the effects of the college attended and the length of the educational program on ASCP Board of Registry Examination Scores. Registry scores were statistically analyzed for all graduates of Butterworth Hospital's (Grand Rapids, Michigan) Medical Technology program for the years 1970-80. Results indicated college differences in student academic preparation, as measured by the certification examination given by the ASCP Board of Registry. There were no statistical differences in average Registry examination scores for students who complete three versus four year educational programs. Other analyses considered sex differences in college grades and Registry exam performance, and the "grade inflation" phenomenon during the period of this study.

Educational Measurement↗
PubMed1980

Phenytoin reversal and prevention of morphine-induced catalepsy in the rat.

The interaction of morphine sulphate and phenytoin was studied with respect to morphine-induced catalepsy in the rat using a previously described method for measuring degree of immobility. As expected, catalepsy developed several minutes after intravenous morphine and lasted for more than ninety minutes. Intravenous phenytoin, 35 mg/kg, given fifteen min prior to or following the administration of morphine, 1 mg/kg, significantly prevented, or reversed, morphine-induced catalepsy. Control experiments revealed that the antagonistic effect was due solely to the morphine-phenytoin interaction. A similar effect was found with naloxone, 0.2 mg/kg. The data are discussed in terms of possible sites of interaction, including synaptosomal calcium metabolism.

Animals↗
PubMed1979

Diazepam and dialysis encephalopathy.

A patient with the clinical and electroencephalographic features of dialysis encephalopathy exhibited dramatic improvement with the initiation of diazepam therapy. Although improvement was sustained for a period of several weeks, her clinical condition eventually deteriorated despite continued treatment with diazepam and dialysis. Dialysis encephalopathy in this patient is compared with other cases recently reported in the medical literature as having a similar dramatic response to diazepam. It is concluded that diazepam transiently reverses a component of the dialysis encephalopathy syndrome, but it does not appear to change the ultimate prognosis for patients with this condition.

Brain Diseases↗
PubMed1979

Clearance of macromolecular and particulate substances from the cerebrospinal fluid system of the rat.

Arachnoid villi in the intracranial dural sinuses constitute the principal sites for absorption of proteins and particulates from the cerebrospinal fluid (CSF) system. Although arachnoid villi in the rat are morphologically less complex than those found in other mammals, their resistance to CSF outflow, as assessed by a graded series of contstant flow manometric infusions, is similar to that found in other species. Moreover, inulin and polystyrene beads, when infused into the spinal subarachnoid space of rats, are rapidly cleared from the CSF system into intracranial dural sinuses. Inulin appeared in sinus blood 3 minutes after onset of infusion and reached concentrations 26 times greater than those found in the systemic circulation; particulate matter in the form of 0.5 micrometer polystyrene beads showed similar efflux characteristics. Hence, the CSF system of the rat is functionally similar to that found in other mammalian species, with arachnoid villi constituting a major efflux route for clearance of macromolecular and particulate substances.

Absorption↗
PubMed1978

Aspirin prophylaxis in migraine.

A prospective double-blind trial of aspirin prophylaxis demonstrated a reduction of more than 50% in headache frequency in 9 of 12 migraine patients. Response to aspirin did not correlate with age, duration of headache history, family history, or platelet ultrastructure. There is some evidence that response to aspirin is associated with raised platelet aggregation. This pilot study indicates that aspirin is effective in migraine prophylaxis.

Adolescent↗
PubMed1978

Regulation of intracranial pressure in rat, dog, and man.

Intracranial resistance and compliance were assessed in the cerebrospinal fluid system of rat, dog, and man by means of low-volume, short-duration infusions of artificial CSF into the subarachnoid space. A family of pressure/time response curves was obtained for each species: at low flow rates, steady-state pressure elevations were associated with normal neurological function; at high flow rates, rapid linear pressure elevations were associated with marked neurological dysfunction. From these curves a mathematical model was developed which describes transport and pressure-dependent valvelike characteristics of the CSF outflow resistance. This resistance shows a progressive phylogenetic change in rat, dog, and man which increasingly enhances the species' abilities to vent fluid from the intracranial cavity into the venous circulation. Arachnoid villi appear to be the major structures modulating sustained, nonlethal elevations of intracranial pressure.

Animals↗
PubMed1978

Intracranial pressure regulation: a comparative model of cerebrospinal fluid systems.

A comparative model of the cerebrospinal fluid (CSF) system in rat, dog and man was derived from manometric data using low volume, short duration infusions into the subarchanoid space in order to describe the mechanisms governing intracranial pressure dynamics. The mathematical model indicates that steady-state elevations of intracranial pressure are regulated primarily by a nonlinear, pressure dependent outflow resistance to CSF reabsorption. While the form of the resistance relationship is similar for the three species tested, differences in the magnitude of CSF outflow parameters are apparent. Model stimulation on a digital computer suggests that parameter changes within the resistance relationship can have a profound effect on the intracranial pressure. In contrast, intracranial compliance acts only to buffer transient changes in volume prior to the establishment of steady-state CSF pressures.

Animals↗
PubMed1976

Long-term prednisone followed by thymectomy in myasthenia gravis.

The present series of thirty patients has led us to certain conclusions concerning the management and treatment of patients with myasthenia gravis. The use of cholinesterase inhibitors alone is reserved for those patients with purely ocular myasthenia whose deficits can be satisfactorily corrected with those agents. Some of those with ocular involvement may be disabled; and in light of our excellent results with that small group, as well as similar findings presented by Fischer et al., patients with disabling or refractory ocular myasthenia should be considered for treatment with prednisone. All other patients with myasthenia are given a course of oral corticosteroids (prednisone) initially at high doses, with subsequent tapering to maintenance, alternate-day low-dose therapy. Cholinesterase inhibitors are used as needed while the patient is receiving corticosteroids. We now anticipate that patients will exhibit sustained improvement within the first two weeks, reaching maximal improvement at about three months. Exacerbations of myasthenic weakness may occur in the early phases of treatment. Such exacerbations have been commonly mild and occur with a mean onset at 5 days, and have a mean duration of 6 days. Most patients have been able to tolerate an alternate-day schedule of prednisone therapy when maintenance levels were achieved. The effective maintenance dose has been determined as the smallest dose of prednisone which allows the patient to maintain maximal improvement. Following the establishment of maximal improvement, patients have been considered for thymectomy. In our experience, the sternum-splitting procedure has been tolerated extremely well by patients exhibiting marked imporvement or remission while on corticosteroids. In those patients where thymectomy is contraindicated, irradiation of the thymus might be considered. Patients are continued on maintenance steroid therapy following surgery for a period of time that has been arbitrary. Currently, we consider an attempt to discontinue steroids at approximately one year reasonable. Should the patient relapse after discontinuation of the medication, oral corticosteroid treatment is reinitiated. Consideration is given to the possibility of recurrent thymus in patients who repeatedly fail to maintain a remission when steroids have been stopped. Our experience has not permitted us to draw firm conclusions concerning how long a time high-dose daily steroid treatment should be continued in patients who show no favorable response to that therapy. Other modes of treatment, such as courses of parenteral ACTH, methyl prednisolone, dexamethazone, or antimetabolites might be considered if there is no response after 12 weeks of high-dose, daily corticosteroid therapy.

Adolescent↗
PubMed1976

Long-term administration of corticosteroids in myasthenia gravis.

Favorable results were obtained in 30 patients with myasthenia gravis treated initially with high daily doses of prednisone and subsequently maintained on lower doses for a protracted period. In 45 incidents of treatment, complete remission occurred in 69 percent, marked improvement in 20 percent, and moderate improvement in 17 percent. Nineteen patients proceeded to thymectomy, with negligible morbidity and sustained improvement. In four patients, it was possible to discontinue prednisone 1 year or more after thymectomy.

Adolescent↗