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Biomedical subjects

J Stein

Publications and source records attributed to J Stein.

At least 523 records · Page 29Linked to original sources
PubMedDate not supplied

The magnocellular theory of developmental dyslexia.

Low literacy is termed 'developmental dyslexia' when reading is significantly behind that expected from the intelligence quotient (IQ) in the presence of other symptoms--incoordination, left-right confusions, poor sequencing--that characterize it as a neurological syndrome. 5-10% of children, particularly boys, are found to be dyslexic. Reading requires the acquisition of good orthographic skills for recognising the visual form of words which allows one to access their meaning directly. It also requires the development of good phonological skills for sounding out unfamiliar words using knowledge of letter sound conversion rules. In the dyslexic brain, temporoparietal language areas on the two sides are symmetrical without the normal left-sided advantage. Also brain 'warts' (ectopias) are found, particularly clustered round the left temporoparietal language areas. The visual magnocellular system is responsible for timing visual events when reading. It therefore signals any visual motion that occurs if unintended movements lead to images moving off the fovea ('retinal slip'). These signals are then used to bring the eyes back on target. Thus, sensitivity to visual motion seems to help determine how well orthographic skill can develop in both good and bad readers. In dyslexics, the development of the visual magnocellular system is impaired: development of the magnocellular layers of the dyslexic lateral geniculate nucleus (LGN) is abnormal; their motion sensitivity is reduced; many dyslexics show unsteady binocular fixation; hence poor visual localization, particularly on the left side (left neglect). Dyslexics' binocular instability and visual perceptual instability, therefore, can cause the letters they are trying to read to appear to move around and cross over each other. Hence, blanking one eye (monocular occlusion) can improve reading. Thus, good magnocellular function is essential for high motion sensitivity and stable binocular fixation, hence proper development of orthographic skills. Many dyslexics also have auditory/phonological problems. Distinguishing letter sounds depends on picking up the changes in sound frequency and amplitude that characterize them. Thus, high frequency (FM) and amplitude modulation (AM) sensitivity helps the development of good phonological skill, and low sensitivity impedes the acquisition of these skills. Thus dyslexics' sensitivity to FM and AM is significantly lower than that of good readers and this explains their problems with phonology. The cerebellum is the head ganglion of magnocellular systems; it contributes to binocular fixation and to inner speech for sounding out words, and it is clearly defective in dyslexics. Thus, there is evidence that most reading problems have a fundamental sensorimotor cause. But why do magnocellular systems fail to develop properly? There is a clear genetic basis for impaired development of magnocells throughout the brain. The best understood linkage is to the region of the Major Histocompatibility Complex (MHC) Class 1 on the short arm of chromosome 6 which helps to control the production of antibodies. The development of magnocells may be impaired by autoantibodies affecting the developing brain. Magnocells also need high amounts of polyunsaturated fatty acids to preserve the membrane flexibility that permits the rapid conformational changes of channel proteins which underlie their transient sensitivity. But the genes that underlie magnocellular weakness would not be so common unless there were compensating advantages to dyslexia. In developmental dyslexics there may be heightened development of parvocellular systems that underlie their holistic, artistic, 'seeing the whole picture' and entrepreneurial talents.

Brain↗
PubMedDate not supplied

Therapeutic monitoring of busulfan in pediatric bone marrow transplantation.

The aim of this study was to describe busulfan disposition in a pediatric population who underwent bone marrow transplantation (BMT). Busulfan administered dose was 1 mg/kg every 6 h for 4 days. Plasma determinations were performed after the first dosing at 0, 15, 30, 60, 90, 120, 180, 240, 300, and 360 min. A noncompartment analysis model for extravascular absorption was used for the pharmacokinetic analysis. To obtain the area under the concentration-time curve (AUC) within the "therapeutic window" of 1,000-1,200 microM x minutes a busulfan dose adjustment Was performed at the fourth dose. Forty-five busulfan pharmacokinetic analyses were performed in 34 children. Eleven children had their dose adjusted [1.19 +/- 0.14) mg/kg] at the fourth dose and the AUC was monitored at the fifth one. The mean AUC +/- SD after the fifth dose (998.1 +/- 189.2 microM x min) was different (p = .006)from that after the first dose (1 mg/kg) (687.63 +/- 166.43 microM x min). Six children had their first AUC into the "therapeutic window," 17 children had their dose adjusted [1.2 (+/- 0.22) mg/kg], but the "adjusted" AUC was not available. These data suggest that it may be reasonable to recommend a busulfan dose of 1.2 mg/kg to achieve the accepted therapeutic target in children undergoing BMT.

Animals↗
PubMedDate not supplied

Hepatitis B vaccination practices in state and federal prisons.

OBJECTIVE: Incarcerated populations are a group at high risk for hepatitis B. About 30% of people experiencing acute hepatitis B virus infection (HBV) have a history of incarceration. Offering routine HBV vaccinations to incarcerated individuals could have a significant effect on public health. The objective of this study is to identify current vaccine practices and the perceived feasibility of routine vaccinations for hepatitis B within correctional settings. METHOD: The authors surveyed the medical directors of state correctional facilities in all 50 states and the federal prison system regarding current HBV vaccine practices. Surveys were faxed or mailed between July 1 and September 1, 2000. RESULTS: Thirty-five states and the federal system responded (response rate = 70.6%). These systems account for 77% of all inmates in federal or state prisons and jails. Two states give hepatitis B vaccine routinely, nine states offer no hepatitis B vaccine, and 26 states and the Federal Bureau of Prisons offer hepatitis vaccine to some inmates. Most states do not spend enough money to vaccinate even those prisoners at highest risk. Under the Vaccine for Children program, 19,520 youths could receive vaccine immediately. According to the respondents, if vaccine were available at no-cost, 25 states and the Federal Bureau of Prisons would routinely offer vaccination to all inmates. CONCLUSIONS: Most correctional systems do not routinely offer vaccine to their incarcerated populations, but would if funds were available. There exists now a unique public health opportunity to prevent a significant proportion of new hepatitis B infections.

Adolescent↗
PubMedDate not supplied

Failure of magnetic resonance imaging to reveal the cause of a progressive cervical myelopathy related to postoperative spinal deformity: a case report.

Imaging studies have achieved a high degree of diagnostic accuracy for many disorders of the spinal cord but have significant limitations. We report on the case of a 49-yr-old man who developed neck pain and arm numbness. He was found to have extensive cervical spondylosis, with spinal cord impingement at C3-4 and cervical radiculopathy. He underwent a C3-7 laminectomy, with transient improvement in his symptoms. During the ensuing year, he developed increased weakness of the upper limbs, evidence of cervical myelopathy, and a severely flexed posture of the cervical spine. Magnetic resonance imaging (MRI) revealed cervical spinal cord atrophy but no evidence of extrinsic spinal cord compression. Cervical flexion and extension films revealed reversal of the normal cervical lordosis without segmental instability. Despite the absence of confirmatory radiologic studies, the patient was felt to have clinical evidence of intermittent compression of his cervical spinal cord attributable to excessive cervical kyphosis, was provided with a cervical collar, and subsequently underwent surgical stabilization. His cervical myelopathy showed marked improvement with these treatments. We conclude that intermittent compression of the spinal cord, occurring in the erect position, was not apparent on the MRI films obtained in the supine position. Flexion and extension films, obtained in the upright position, documented his abnormal cervical anatomy but did not reveal substantial segmental instability. Spinal deformity without segmental instability may cause cervical myelopathy after multilevel cervical laminectomies without evidence of extrinsic compression on MRI.

Braces↗
PubMedDate not supplied

Medical student referral patterns for musculoskeletal disorders.

The purpose of this study was to determine the relationship between medical student knowledge and exposure to physiatry and the student's referral patterns for musculoskeletal disorders. Surveys were mailed to senior medical students at five United States medical schools across the country with a response rate of 26% (n=191). Five common musculoskeletal and neurologic disorders were presented as clinical vignettes and the student was asked to assume the role of a primary care physician and refer the patient to one of eight specialists listed. A section to assess the student's subjective overall knowledge and exposure to these fields was also included. Physiatrists received 27% of the referrals for evaluation and treatment of chronic low-back pain, 3% of the referrals for acute low-back pain, 10% of the referrals for carpal tunnel syndrome, 22% of the referrals for an industrial medicine injury, and 20% of the referrals for a sports medicine injury. The frequency of physiatry referrals for three of the five cases was significantly correlated (P < 0.05) with the student's overall knowledge of physical medicine and rehabilitation (PM&R). The presence of a department of PM&R at the student's school, however, did not have a significant impact on the rate of referrals. The results indicate that senior medical students referral patterns are strongly influenced by knowledge of PM&R. This suggests that focusing efforts on increasing this awareness may be an effective means of increasing referrals to physiatry in the future.

Adolescent↗
PubMedDate not supplied

Tributyrin, a butyrate precursor, impairs growth and induces apoptosis and differentiation in pancreatic cancer cells.

BACKGROUND: The aim of this study was to investigate whether tributyrin, a natural butyrate pro-drug, as well as butyrate itself could affect growth, differentiation and apoptosis in two human pancreatic cancer cell lines in culture. MATERIALS AND METHODS: Proliferation was studied by cell counting using crystal violet staining. Cell differentiation was assessed by measuring the alkaline phosphatase activity and cell death by DAPI nuclear staining. RESULTS: In MiaPaca-2 cells both tributyrin and butyrate reduced growth, with IC50 values of 1.1+/-0.2 mmol/ and 3.6+/-0.7 mmol/L respectively. Both 1 mmol/L tributyrin and 3 mmol/L butyrate induced a similar degree of apoptosis in MiaPaca-2 and Capan-l cells and stimulated differentiation in Capan-l cells equally. CONCLUSION: Our data may provide a rationale for the therapeutic use of peroral tributyrin in patients with pancreatic cancer, because this drug enables plasma concentrations of butyrate which inhibit growth, induce differentiation and cause apoptosis in pancreatic cancer cells.

Apoptosis↗
PubMedDate not supplied

[Adenocarcinoma of the esophagogastric junction (AEG-tumor). Review of the literature].

Due to an increase in the prevalence of cancer of the esophagogastric junction as well as in the knowledge of the origin and factors associated with the disease, we reviewed the definition according to the Siewert Stein classification, staging and surgical approach to early and advanced cases, as well as the introduction of new surgical techniques, adjuvant treatment and the use of PET Scan in the evaluation of response to neoadjuvant treatment; with more encouraging results.

Adenocarcinoma↗