Prenatal neurochemistry of cocaine.
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Aging↗
Biomedical subjects
J S Meyer
Publications and source records attributed to J S Meyer.
Graphical representation of survival curves associated with a binary non-reversible time dependent covariate.
The use of time dependent covariates has allowed for incorporation into analysis of survival data intervening events that are binary and non-reversible (for example, heart transplant, initial response to chemotherapy). We can represent this type of intervening event as a three-state stochastic process with a starting state (S), an intervening state (I), and an absorbing state (D), which usually represents death. In this paper we present three procedures for calculating survivorship functions which attempt to display the prognostic significance of the time dependent covariate. The first method compares survival from baseline for the two possible paths through the stochastic process; the second method compares overall survival to survival with state I removed from the process; and, the third method compares survival for those already in state I at a landmark time x to those in state S at time x who will never enter state I. We develop discrete hazard estimates for the survival curves associated with the three methods. Two examples illustrate how these methods can yield different results and in which situations one might employ each of the three methods. Extensions to applications with reversible binary time dependent covariates and models with both baseline and time dependent covariates are suggested.
Data Interpretation, Statistical↗
The current radiologic management of intussusception: a survey and review.
To determine what practices are being utilized in the management of intussusception, a survey was sent to chairpersons of 64 Pediatric Radiology departments in the United States and Canada. There was a 92% response rate. Barium is used in 97% of departments and is the most commonly used contrast-agent in 64%. Water-soluble contrast is used in 83% of departments and air in 50%. In high-risk patients, water soluble contrast is used in 71% of departments, air in 28% and barium in 24%. Glucagon, pre-exam antibiotics, and pre-exam sedation are not used regularly in a majority of departments. The radiologic management of intussusception is more varied than only a few years ago. Use of water-soluble contrast and air have increased, while barium use is less routine.
Barium Sulfate↗
Primary megaureter in infants and children: a review.
Primary megaureter is a common cause of obstructive uropathy in children. The imaging studies and records of 75 infants and children with primary megaureter seen at Children's Hospital were reviewed. We describe our findings and illustrate the clinical presentations, diagnosis, and treatment of this entity.
Child↗
White matter lesions in the elderly.
The advent of neuroimaging has brought medical attention to the frequency of unsuspected white matter lesions in the brains of elderly people. In 1987 Hachinski suggested the term "leuko-araiosis" to identify such white matter abnormalities detected by computed tomography and magnetic resonance imaging to emphasize that their etiology and clinical relevance require clarification. Since then, leuko-araiosis has been recognized among approximately ten percent of apparently normal, elderly people over age sixty-five. The severity and frequency of leuko-araiosis increases with advancing age, risk factors for stroke, history of strokes particularly of the lacunar type and dementia of both the vascular and Alzheimer type. Current concepts concerning the pathogenesis and neurological concomitants of leuko-araiosis are reviewed. The etiology of leuko-araiosis may be heterogeneous but is most likely ischemic in nature. However, as white matter lesions progress among the elderly they are likely to become associated with cognitive impairments and motor dyspraxias presumably resulting from cortico-subcortical disconnections, particularly involving the frontal cortex and basal ganglia and may themselves be considered a radiological "risk factor" or precursor for dementia.
Aged↗
Leuko-araiosis and cerebral hypoperfusion compared in elderly normals and Alzheimer's dementia.
OBJECTIVE: To elucidate the pathogenesis of leuko-araiosis in patients with Alzheimer's disease by utilizing CT densitometry of the brain and measurements of local perfusion in order to quantify the extent of leuko-araiosis and local hypoperfusion compared with similar measurements made among age-matched normal volunteers. DESIGN: Cross-sectional case-control study. SETTING: Out-patient visits to a specialized laboratory located in a large hospital facility. PATIENTS: Eighteen elderly patients with probable dementia of Alzheimer type (DAT, aged 71.8 +/- 5.1 years) and 17 neurologically and cognitively normal, age-matched volunteers (aged 68.2 +/- 9.6 years) were admitted to the study according to established criteria. INTERVENTION: None MAIN OUTCOME MEASURES: Cerebral blood flow (mL/100 g brain/min) estimated by the xenon inhalation CT-CBF method correlated with volume percentage ratio (%) measured by CT densitometry for leuko-araiosis, compared to normal white and gray matter. RESULTS: Perfusion values for frontal and occipital white matter as well as frontal, parietal, temporal, and occipital cortex were all decreased in DAT patients. Ratios for leuko-araiosis to total brain tissue volumes were greater among patients with DAT compared with age-matched normal volunteers. White matter perfusion in zones of leuko-araiosis was decreased to a similar degree in both DAT and elderly normal volunteers. CONCLUSIONS: Perfusion is reduced to the same degree in regions of leuko-araiosis in elderly normals as in DAT patients, but the extent of leuko-araiosis is greater among DAT patients and presumably contributes to cognitive impairments.
Aged↗
Pneumatic versus hydrostatic reduction of intussusception.
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Adolescent↗
Patterns of cerebral hypoperfusion compared among demented and nondemented patients with stroke.
BACKGROUND AND PURPOSES: No reports are available that compare local cerebral perfusion among groups of patients suffering from multiple cerebral infarctions with and without cognitive impairments. The present study was designed to correlate changes in regional cerebral perfusion that may lead to dementia among patients with multiple cerebral infarctions by comparing measurements of local cerebral blood flow. METHODS: Local perfusion was measured using xenon-contrasted computed tomographic scanning among two groups of patients who had suffered from multiple cerebral infarctions: Group D (n = 12) were demented and had severe cognitive impairments, and group I (n = 11) were cognitively intact. Results were compared with similar measurements among neurologically and cognitively normal, age-matched volunteers (group N, n = 16). RESULTS: Mean local perfusion values were reduced among both groups with cerebral infarctions but to a more marked degree in group D (p less than 0.05). Perfusion of cerebral white matter was diffusely and severely reduced in group D (p less than 0.05) but was mildly reduced only in frontal and capsular white matter in group I (p less than 0.05). Perfusion of cerebral cortex was reduced in frontal (p less than 0.01) and temporal (p less than 0.01) regions among both groups but to a significantly greater degree in group D subjects (frontal, p less than 0.05; temporal, p less than 0.01), who also showed hypoperfusion of the occipital cortex (p less than 0.05), apparently because of underlying leukoaraiosis and cortical disconnections. Perfusion of the basal ganglia was reduced to the same degree among both groups of stroke patients (p less than 0.01). CONCLUSIONS: Leukoaraiosis with white matter hypoperfusion appears to be an important determinant for cognitive impairments among patients with multiple cerebral infarctions.
Aged↗
Diagnosis of liver disease in children: value of MR angiography.
We retrospectively studied the clinical use of MR angiography, a gradient-echo technique susceptible to motion, in the preoperative evaluation of the hepatic vasculature in children with liver disease. Twenty imaging examinations were performed in 18 patients 3 months to 10 years old (mean, 2.3 years). Eleven patients had liver tumors and seven had cirrhosis associated with biliary atresia, cystic fibrosis, and short-bowel syndrome. Respiratory motion artifacts were present in most patients, but all MR angiographic studies were technically adequate. Comparing MR angiograms with spin-echo images, we found that vascular visualization was better with MR angiography in 12 cases (60%), equal in five (25%), and worse in three (15%). In 10 of 20 cases, MR angiography provided additional vascular information not present on spin-echo images. MR angiography is a useful adjunct to spin-echo imaging for assessing hepatic vascular anatomy in children with liver disease.
Angiography↗
Exogenous tyrosine potentiates the methylphenidate-induced increase in extracellular dopamine in the nucleus accumbens: a microdialysis study.
Previous work has shown that the synthesis and release of dopamine may, under certain conditions, be influenced by an increase in the availability of its amino acid precursor, tyrosine. To examine whether exogenous tyrosine could potentiate the methylphenidate-induced increase in extracellular dopamine, male rats were implanted with microdialysis probes aimed at the right nucleus accumbens. Samples were collected from awake animals beginning 22 h after surgery. A repeated measures design was used involving the continuous collection of 20-min samples for a 4-h period once a day for 3 consecutive days. On a given day, an animal was infused with methylphenidate, tyrosine, or methylphenidate plus tyrosine. Periods of infusion with the active compounds were preceded and followed by baseline conditions, and treatments were counterbalanced to control for possible order effects. Methylphenidate plus tyrosine significantly increased extracellular levels of dopamine in comparison to drug alone. This effect was long-lasting, persisting into the post-treatment sampling period and peaking 40 min after the peak induced by methylphenidate alone. Tyrosine alone induced a small but significant increase in extracellular dopamine in the absence of any treatment to accelerate the firing of dopamine cells. These findings may have implications for the treatment of attention deficit hyperactivity disorder.
3,4-Dihydroxyphenylacetic Acid↗
[Does alternative medical equipment result in pacemaker dysfunction?].
Employment of alternative therapeutic measures is increasing in Denmark. Some of this equipment employs magnetic fields in the therapeutic strategy. This may involve interference with the function of electronic equipment. Electronic interference may, in certain situations, influence pace-maker function. In the worst cases, it may be imagined that the situation may endanger life for persons who are dependent on pace-makers. When a pace-maker is exposed to a magnetic field of a certain strength, the type of pacing is changed to a fixed frequency. Some pace-maker types carry out a built-in test programme when exposed to magnetic influence (vario- or threshold test). The magnetic influence may involve discomfort for the wearer of the pace-maker, but does not endanger life. Investigation of stationary magnetic fields from alternative medical equipment resulted in disturbance of pace-maker function in an isolated case. Pulsating magnetic fields may result in possible induction of electric current which may be wrongly interpreted by the pacemaker. The results of this may be that the pace-maker does not send out pace impulses. As protection from continuous electric noise, pace-makers have a built-in electronic safety circuit (dual-demand). When this is activated, the pace-maker will stimulate with a basic frequency. It is recommended that equipment which employs magnetic fields in treatment should be measured before being employed on pace-maker wearers.
Complementary Therapies↗
Regional heterogeneity in breast carcinoma: thymidine labelling index, steroid hormone receptors, DNA ploidy.
We examined multiple samples of 65 primary breast carcinomas larger than 1 cm in diameter for thymidine labelling index (TLI), DNA index (DNAI, a measure of cellular DNA content by flow cytometry), and estrogen (ER) and progesterone (PgR) receptors by radioligand-binding. One or more axillary metastases were also assayed in 11 patients. Two to 15 samples were successfully assayed for TLI from 59 tumors, 2-31 samples for DNAI from 61 tumors, and 2-15 samples from 55 tumors for ER and PgR. Criteria for heterogeneity were excess inter-sample variance in comparison with intrasample variance at the p less than 0.05 level for TLI and DNAI, and variation of clinically significant magnitude in assay results for ER and PgR. Sixty-one percent of tumors were heterogeneous for TLI, 26% for DNAI, 24% for ER and 40% for PgR. High TLI disposed toward heterogeneity for TLI itself (p = 0.06), for ER (p = 0.04), and for PgR (p = 0.007). Young age favored heterogeneity for TLI (p = 0.12), ER (p = 0.002), and PgR (p = 0.04). Heterogeneity for DNAI was not related to age and TLI status but was more common in larger tumors (p = 0.08). After consideration of relationships between TLI, age, size, ER and PgR, TLI rather than age appears to be the more important determinant of heterogeneity for receptors. High TLI could lead to heterogeneity through increased numbers of cell divisions that favor emergence of variant stemlines, or by causing local vascular and humoral disparities through rapid growth. Regional heterogeneity can explain erroneous prognostic predictions in approximately 10% to 20% of breast carcinoma patients. We recommend multiple sampling of large breast carcinomas and analysis of axillary metastases for study of tumor markers.
Adult↗
Relationship between c-erbB-2 immunoreactivity and thymidine labelling index in breast carcinoma in situ.
The relationship between the presence of the c-erbB-2 protein, demonstrated immunohistochemically with antibody 21N, and thymidine labelling index (TLI) has been studied in the in situ component of 70 cases of carcinoma of the breast. A significant association was found between high TLI and positive staining. Twenty of the 70 cases stained (29%) and of those that were stained 75% had a high TLI; 43% of those with a high TLI stained positively but only 14% of those with a low TLI stained positively. Strong correlations were seen between nuclear size and histological pattern and both 21N staining and TLI. The majority of carcinomas of comedo pattern with large nuclei were 21N positive and had a high TLI, whilst those with small nuclei and a predominantly cribriform/micropapillary appearance did not stain and had a low TLI. In tumours of mixed histological pattern there was less concordance between staining and TLI. The significance of these findings in relation to the biological behaviour of these tumours and their clinical management is discussed.
Breast Neoplasms↗
Cerebral hypoperfusion correlates with mild and parenchymal loss with severe multi-infarct dementia.
Relative contributions of two potential pathogenetic factors for cognitive impairments among patients with multi-infarct dementia (MID) are reported. Cognitive test scores were correlated with measures of cerebral hypoperfusion and loss of brain parenchyma. Local cerebral blood flow values were determined utilizing stable xenon contrasted computed tomography and volumes for brain parenchyma were estimated from ratios of volumes of infarcted brain plus cerebrospinal fluid/total intracranial volume measured on the same CT slices among two groups of patients, one with mild and the other with severe MID. A total of 26 demented patients with multiple cerebral infarcts were divided into 2 index groups, one with mild and the other with severe MID (mild MID, CCSE greater than or equal to 15, n = 16; severe MID, CCSE less than 15, n = 10). Results were compared with similar measures among age-matched neurologically normal volunteers (n = 14). Ratios for volumes of lost brain parenchyma were significantly higher among severe MID patients than among age-matched normal volunteers, whereas estimates of brain loss among patients with mild MID did not differ from elderly normal volunteers. In patients with mild MID, LCBF values for cortical gray matter were decreased compared with age-matched normal volunteers. Results suggest that chronic cerebral hypoperfusion is an important determinant for mild dementia among patients in the early stages of MID, but volumes of lost cerebral parenchyma due to cerebral infarctions is an important determinant for advanced stages of MID.
Aged↗
Regional patterns of brain growth during the first three weeks following early adrenalectomy.
Day 11 adrenalectomized (ADX) and sham-operated control rats were compared with respect to overall and regional brain growth and DNA content at 1, 2, and 3 weeks postsurgery. Possible treatment effects on the rate of postnatal cell loss were also assessed by injecting the animals with 3H-thymidine on day 2 postnatal (9 days prior to surgery) and subsequently measuring the amount of radiolabelled DNA remaining in various brain regions at each time point. Adrenalectomy led to reliable increases in cerebral cortex and midbrain-diencephalon weights within 1 week postsurgery, whereas cerebellum, hippocampus, and overall brain weights were not significantly elevated until 1 or 2 weeks later. The effects of adrenalectomy on tissue DNA content were likewise regionally dependent. According to the 3H-thymidine results, there was no significant influence of adrenalectomy on the loss of previously labelled DNA. In conclusion, the timing of brain growth acceleration following adrenal removal is regionally specific, with the most rapid effects occurring in the cortex and midbrain-diencephalon. Furthermore, adrenalectomy-induced increases in brain cell number appear to depend primarily on increased cellular genesis (as previously demonstrated) rather than decreased cell death.
Adrenal Glands↗
Cognitive recovery correlates with long-term increases of cerebral perfusion after head injury.
Prospective measurements of cerebral blood flow (CBF) and Cognitive Capacity Screening Examination (CCSE) were obtained following head injury among 42 patients for a mean total follow-up interval of 10 years. Clinical data obtained at the time of injury and detailed neurological examinations at each follow-up visit were correlated with serial CBF and CCSE scores. Comparisons of the group of patients who cognitively improved (n = 32) were made with the group that did not (n = 10). Of the total group, 76% showed cognitive improvements for as long as 10 years after injury, with CBF increases toward normal. Predictors for long-term cognitive improvements include: higher initial Glasgow Coma Scales, earlier recovery from coma, absence of signs of brain stem injury, and improvements of cerebral perfusion and autoregulation. Failure to improve correlated with low initial Glasgow Coma Scales, signs of brain stem injury, and persistent impairments of cerebral perfusion.
Adolescent↗
Cell kinetics by bromodeoxyuridine labeling and deoxyribonucleic acid ploidy in prostatic carcinoma needle biopsies.
We studied 63 prostate carcinomas in needle biopsies after labeling in vitro by incubating the entire biopsy specimen with tritiated thymidine or bromodeoxyuridine before fixation. Biopsies from 176 patients were labeled, of which 98 were benign and 78 were carcinomas (15 carcinomas were excluded because of scant tissue). The procedure did not interfere with histological diagnosis. Median labeling index was 0.87% (range 0.1 to 29.3%). A labeling index exceeding 3% was unusual but it may indicate the potential for rapid clinical progression. Deoxyribonucleic acid (DNA) flow cytometry was performed on the last 44 carcinomas using cells shed by the prostatic needle biopsy tissue samples during transportation to the pathology laboratory. A sufficient number of cells were obtained for analysis in 37 cases, of which 6 were DNA aneuploid. Labeling index correlated with Gleason histological grade and score, and data from the 6 DNA aneuploid carcinomas suggest association between DNA aneuploidy and a high labeling index. Estimates of percentage of S-phase cells by flow cytometry did not correlate with variables other than DNA index, and appear to have been affected by a high noise-to-signal ratio (few proliferative cells relative to cellular debris) and inability to discriminate between benign and carcinomatous cells.
Aged↗
Does diaschisis have clinical correlates?
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Agnosia↗