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Biomedical subjects

J M Freeman

Publications and source records attributed to J M Freeman.

At least 19 recordsLinked to original sources
PubMed1992

What have we learned from febrile seizures?

What have we learned from febrile seizures? We have learned that there is a natural history to different seizure types, what some have taken to calling "seizure syndromes." We have learned that understanding these "natural histories" may be helpful in making decisions about treatment. We have learned that seizures themselves, while unpleasant, may not be harmful and don't always have to be treated. We have learned that sometimes the treatment is worse than the disease and that the side effects of medication may have more consequences than the occurrence of another seizure. We have learned that the determination of the "risks" and consequences of the seizures should be made by the patient or the family, and that they may assess the risks and benefits quite differently than the physician. Similarly, the benefits and consequences of anticonvulsant medication may be assessed quite differently by different people. We have learned that all seizures do not need to be treated, and we have learned that those that are treated should be treated for the shortest time possible. I believe that these are important lessons that should affect our management of afebrile seizures as well.

Age Factors↗
PubMed1991

Biochemical and molecular characterization of variant pyruvate kinase enzymes and genes from three patients with red blood cell pyruvate kinase deficiency.

Pyruvate kinase (PK) from red blood cells (RBC) of three patients with nonspherocytic hemolytic anemia due to PK deficiency was characterized according to internationally standardized methods. The variant enzymes, which were designated PK 'Memphis', PK 'Bartlett', and PK 'Pontotoc', had 11, 60, and 61%, respectively, of the normal enzyme activity. All variant PK enzymes had increased thermolability. Compared with control, Km (PEP) were 200-300% greater for PK 'Memphis', 50% less for PK 'Bartlett' and 300-400% greater for PK 'Pontotoc'. The Km (ADP) were 40 and 300% greater than normal for PK 'Bartlett' and PK 'Pontotoc', respectively. All variants required higher than normal concentrations of the allosteric modifier, fructose-1,6-diphosphate, to achieve 50% activation of maximal enzyme activity. To define the molecular basis of the gene defect, DNA samples from these patients were examined for restriction-fragment-linked polymorphisms. No differences were observed in the structure of the patients' PK genes compared with a normal control. These results are consistent with a mutation in coding sequences, rather than a large insertion, deletion or rearrangement of genetic information, as the underlying genetic defect that accounts for the altered enzyme properties in these PK-deficient patients.

Enzyme Stability↗
PubMed1991

Scleral stretch incision for cataract surgery. A technique for no-suture closure and control of astigmatism.

The scleral stretch incision for cataract surgery by phacoemulsification is a three-plane, multiwidth corneal incision. It is a refinement of the scleral pocket incision. It uses the elasticity of scleral tissue for insertion of a standard (6.0 mm) poly(methyl methacrylate) intraocular lens (IOL) through a smaller (4.5 mm) incision. The technique also allows spontaneous wound closure without a suture. Advantages of the scleral stretch incision technique are an efficient, watertight entry into the eye for phacoemulsification and IOL insertion and no-suture closure. Early clinical observations indicate that the scleral stretch incision minimizes surgically induced corneal astigmatism.

Astigmatism↗
PubMed1990

An index for estimating probabilities of surgical success for cataract patients with retinal disease.

Patients with cataracts and coincident retinal disease are at increased risk for unsuccessful cataract surgery. We developed a method for estimating probabilities of surgical success for older cataract patients with retinal disease. Using data from a prospective study of cataract surgery outcomes, 36 patients with both cataracts and retinal disease were identified, 13 of whom attained surgical success with 20/40 or better vision 4 months after surgery. Age, presurgical Snellen letter acuity, location of retinal lesions, and presurgical visual function in everyday life (newspaper reading or television viewing) were all reliable correlates of surgical outcome. These data were analyzed using multiple logistic regression to develop a clinical index combining presurgical Snellen letter acuity, location of retinal lesions, and age to predict surgical success. The resulting index demonstrated 83% sensitivity and 85% specificity in sample data, correctly predicting 83% of patients (predictive value positive: 73%; predictive value negative: 90%).

Activities of Daily Living↗
PubMed1990

Central nervous system vasculitis after chickenpox--cause or coincidence?

A 7.5 year old boy, known to have a seizure disorder, presented with an infarct in the left middle cerebral artery territory, 10 weeks after severe chickenpox. Immunofluorescent antibody titre to the varicella zoster virus in the cerebrospinal fluid was 1:32. Cerebral angiography showed evidence of focal vasculitis. He presented again seven months later with an acute exacerbation of seizures. Magnetic resonance imaging of the brain showed an old posterior extension of the infarct, but a repeated angiography demonstrated an improvement in the vasculitic process. Cerebrospinal fluid antibody titre was again 1:32. Although this may have been an unfortunate coincidence, a possible association between chickenpox and vasculitis, similar to that reported with herpes zoster, and with potentially significant clinical implications, should be considered. As a definite proof can be obtained only by a brain biopsy, however, which is generally not indicated in such cases, only additional clinical reports can lead to delineation of this association as a definite entity.

Brain Diseases↗
PubMed1990

The paralysis associated with myelomeningocele: clinical and experimental data implicating a preventable spinal cord injury.

Paralysis seen in children with myelomeningocele has been attributed to congenital myelodysplasia. We suspected that paralysis may be due in part to a spinal cord injury caused by exposure of the neural tube to the amniotic fluid. This hypothesis was tested using a fetal rat model of surgically created dysraphism. Each pup from the experimental group of rats in which the spinal cord was intentionally exposed to the amniotic fluid was born with severe deformity and weakness of the hind limbs and tail. Control fetal rats, subjected to the same procedure without directly exposing the spinal cord to the intrauterine environment, were normal at birth. Histological studies of the exposed spinal cord revealed extensive erosion and necrosis, findings similar to those described in children with myelomeningocele. We therefore propose a "two-hit" hypothesis to explain the paralysis seen in children with myelomeningocele: congenital myelodysplasia complicated by an intrauterine spinal cord injury. Intrauterine protection of the exposed spinal cord might prevent some or all of the paralysis. The possible implications of these findings for the future treatment of myelomeningocele are discussed.

Amniotic Fluid↗
PubMed1989

No-fault cerebral palsy insurance: an alternative to the obstetrical malpractice lottery.

Sixty percent of malpractice premiums paid by obstetricians go to cover suits for alleged birth-related cerebral palsy (CP). Yet substantially less than half of that money goes to CP victims, and less than 10 percent of children with CP receive any compensation at all from tort suits. This paper proposes a system that would compensate all children born with CP for most handicap-related expenses, in exchange for which the children would be foreclosed from bringing suits alleging birth-related malpractice. Malpractice would be policed by a state board, which would investigate all CP cases. This proposal would be more equitable than current systems. It would also be less expensive, since it would avoid costly litigation and decrease the cost of obstetrical malpractice insurance.

Birth Injuries↗
PubMed1988

A clinical index for predicting visual acuity after cataract surgery.

We developed a clinical index for predicting postoperative visual acuity of cataract patients and cross-validated it using data from 182 patients aged 70 years and older. The index consisted of four statistically combined indicators: age, preoperative visual acuity, frequency of reading, and comorbidity. Validation of the index included comparisons to two standard technical instruments for measurement of retinal visual acuity. For the clinical index, 72% of predictions were accurate within one Snellen line of postoperative visual acuity compared to 37% using a laser interferometer and 33% using a potential acuity meter. Testing of the clinical index's external validity using data from 111 patients in a different ophthalmology clinic disclosed 61% of predictions accurate within one Snellen line.

Aged↗
PubMed1988

Predictions of outcomes from cataract surgery in elderly persons.

To determine how well visual outcomes of cataract surgery can be predicted from acuity estimations by visual instruments and an ophthalmologist, the authors compared predictions of postsurgical visual acuity with the measured acuity at 4 months in 82 elderly persons. Comparisons were made between the potential acuity meter (PAM), laser interferometer (LI), and an ophthalmologist, who predicted the final vision before surgery using screening visual information, including PAM, LI data, and results of the patient's examination. Neither instrument alone was successful in predicting postsurgical acuity +/- 1 contiguous Snellen chart line (bivariate correlation [r] = 0.03 for PAM and 0.07 for LI). The ophthalmologist was the most accurate predictor of acuity within 1 line (r = 0.41, p less than or equal to 0.001). These results indicate that the PAM and LI did not independently predict postsurgical vision in elderly cataract patients, but results of a clinical examination markedly improved the accuracy of predictions.

Aged↗