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Biomedical subjects

J Cohn

Publications and source records attributed to J Cohn.

At least 19 recordsLinked to original sources
PubMed1992

Comparison of error patterns produced by scopolamine and MK-801 on repeated acquisition and transition baselines.

An understanding of the differential role of cholinergic and glutaminergic systems may be limited by the failure to move the analysis of learning impairments beyond an assessment of changes in overall accuracy. This paper reports the results of two studies in which the effects in rats of scopolamine (0.5-3.0 mg/kg IP), a cholinergic antagonist, and MK-801 (0.05-0.3 mg/kg IP), an NMDA-receptor antagonist, were compared in two different repeated learning procedures and the nature of the underlying error patterns produced by each was evaluated. The first study examined drug effects upon a repeated sequence acquisition procedure and found that while both drugs decreased overall accuracy in a dose-dependent manner, the predominant error pattern varied significantly with drug; scopolamine primarily produced skipping errors within the sequence, whereas MK-801 more prominently increased perseveration on the first and second members of the sequence. In the second study, which used a repeated transition procedure, both drugs again significantly decreased overall accuracy in a dose-dependent manner, but no consistent differences in error patterning produced by the drugs were observed. Thus, while both cholinergic and NMDA systems play a role in learning, the behavioral processes underlying the changes in overall accuracy may differ, as indicated by the differential patterns of errors produced by scopolamine and MK-801 in the repeated acquisition baseline. Furthermore, the observed differences in the underlying behavioral processes of scopolamine and MK-801 in the repeated acquisition but not on the repeated transition procedure suggest that each of the two drugs may affect more than one of the variables controlling behavior, with the relative impact of drug-related changes in controlling variables depending upon the operative contingencies of the learning task.

Animals↗
PubMed1992

Lead retards development of Drosophila melanogaster.

1. Lead (Pb) is a ubiquitous environmental toxicant which has been reported to have growth-retarding effects. That premise was examined in the current study of the effects of developmental exposure to Pb on the maturation of the fruitfly Drosophila melanogaster. 2. Flies were raised from egg to adulthood in media to which 0, 100, 250, or 500 ppm Pb acetate added. 3. There was a dose-dependent delay of maturation but no apparent effect on survival to adulthood. There were no significant differences in this effect between male and female flies. 4. Weights of fly offspring and their fecundity were not related to increasing exposure levels, suggesting that the delays were not due to gross nutritional deficits. 5. Analyses of Pb content indicated exposure-dependent body burdens of Pb in flies. Timed analyses of the Pb content of media itself indicated a heterogeneous distribution of Pb in the media, suggesting some precipitation of Pb at the highest exposure, occurring primarily during the first hour. 6. The mechanistic bases of the Pb-induced retardation of D. melanogaster development remain unknown, but it is concluded that because of the extensive body of knowledge on D. melanogaster genetics, molecular biology, and developmental biology, this procedure could serve as a model system for further study of the developmental consequences of exposure to Pb or other toxicants. 7. Environmental Pb exposure resulting in retarded development could have deleterious repercussions for insect populations exposed chronically to high levels of Pb.

Animals↗
PubMed1991

Regional perinatal care in crisis: a case study of an urban public hospital.

Regionalized perinatal care is intended to guarantee pregnant women and neonates access to appropriate care regardless of ability to pay. Its effectiveness depends on the willingness of hospitals to transfer high-risk patients according to established protocols and affiliations. This study examines maternal transfers (n = 896) to Cook County Hospital (CCH), a public facility and a designated perinatal center in Chicago. In 1987 and 1988, the majority (68%) of maternal transfers to CCH came from out-of-network hospitals, and 52% of these came directly from another perinatal center. The data indicate that 62% of the out-of-network transfers who delivered were medically high-risk. The study also documents the transfer of women in active labor, a violation of federal law. The term "perinatal dumping" is introduced to mean the transfer of high-risk pregnant women between hospitals for economic rather than medical reasons. Strategies for safeguarding the integrity of regionalized perinatal care are discussed.

Adolescent↗
PubMed1990

Ion channels in the nuclear envelope.

Cell nuclei are capable of partitioning a wide variety of molecules from the cytosol, including macromolecules such as proteins and RNA, and smaller peptides, amino acids, sugars and Na+ and K+ ions, all of which can be accumulated in or excluded from the nuclear domain. There are two mechanisms behind this compartmentalization: selective retention of freely diffusible molecules, and selective entry through the nuclear envelope. It is generally accepted that the nuclear envelope restricts only the larger molecules. Here we apply the patch-clamp technique to isolated murine pronuclei and show that the nuclear envelope contains K(+)-selective channels which have multiple conductance states, the maximal conductance being 200 pS. These channels, which contribute to the nuclear membrane potential, may be important in balancing the charge carried by the movement of macromolecules in and out of the nucleus.

Animals↗
PubMed1990

Dialysis-induced respiratory acidosis.

The inability to increase alveolar ventilation can lead to CO2 retention and acute respiratory acidosis in patients with ventilatory limitation. In this case, a young woman receiving maximum ventilatory support was unable to excrete excess CO2, associated with increasing dianeal concentrations of peritoneal dialysis. Since the patient's lung disease had necessitated a large amount of ventilatory support, the patient was unable to increase VE appropriately to handle excess CO2. Peritoneal dialysate was an additional source of carbohydrates. Peritoneal dialysate is an additional carbohydrate source that may result in hypercapnia and respiratory acidosis in patients with respiratory compromise. To our knowledge, this is the first case report in an adult which demonstrates that peritoneal dialysis with high glucose loads produced an acute respiratory acidosis that was reversed by decreasing the glucose concentrations in the dialysate. Excess CO2 production should be considered with respiratory disorders associated with dialysis.

Acidosis, Respiratory↗
PubMed1989

Pre- and postpuberal medial preoptic area lesions and maternal behavior in the rat.

The ability of female rats to express maternal behavior following pre- or postpuberally-administered lesions of the medial preoptic area (MPOA) was investigated. Female Sprague-Dawley rats were electrolytically or sham-lesioned at either 28-30 days of age or 65-70 days of age and housed together in groups of 6-8 in "enriched" environments. Subsequently, the animals were mated and moved to individual cages just prior to parturition. Indices of maternal proficiency included nest ratings, pup retrieval time, percentage of pups with milk in their stomachs, and percentage of pup mortality. All animals in which lesions had substantially damaged the MPOA demonstrated significant deficits in all indices. Age at which the lesion was administered had no effect. In contrast to the recovery of male sexual behavior that has been reported for rats following prepuberally administered MPOA lesions, no recovery of maternal behaviors was seen in this study. Reasons for this lack of recovery may include the greater complexity of physiological and behavioral processes involved in maternal behavior in comparison to the rather stereotypical response patterns of male sexual behavior.

Aging↗
PubMed1989

Multiple calcium-mediated effector mechanisms regulate chloride secretory responses in T84-cells.

Free cytosolic Ca2+ [( Ca2+]i) has been implicated as a second messenger mediating the ion transport effects of carbachol, histamine, taurodeoxycholate, ionomycin, and 4-bromo-A23187 (4-BrA23187) in T84-cells. In this study, we correlated short-circuit current (Isc, reflective of Cl- secretion) and [Ca2+]i responses in T84-cell monolayers stimulated by these agents to evaluate the role of [Ca2+]i in Cl- secretory responses. Time-course studies showed that the duration of [Ca2+]i and Isc responses did not correlate with one another. Isc responses were more prolonged than [Ca2+]i responses with carbachol and histamine (both derived [Ca2+]i partly from intracellular sources), less prolonged than [Ca2+]i with taurodeoxycholate, and continued to increase after [Ca2+]i stabilized with ionomycin and 4-BrA23187. Isc and [Ca2+]i responses to histamine and carbachol were additive. A comparison of the magnitude of [Ca2+]i and Isc responses in cells stimulated by different agonists showed that the change in [Ca2+]i accompanying equivalent Isc responses varied greatly, suggesting that secretagogues vary in their dependency on [Ca2+]i. These findings suggest the existence of multiple [Ca2+]i-mediated effector mechanisms or the existence of multiple mediators that augment or attenuate the action of [Ca2+]i.

Calcium↗
PubMed1984

Serum ferritin and iron status of children in the Faroe Islands.

Iron status was assessed by measurement of serum ferritin (S-ferritin), transferrin saturation and haemoglobin (Hb) in 270 healthy Faroese children (153 males, 117 females) 4, 8 and 13 years old. There were no significant differences between the three variables in boys and girls. Geometric mean S-ferritin increased from 16 micrograms/l in 4-year-old children to 21 micrograms/l in 8-year-old (P less than 0.01) and 25 micrograms/l in 13-year-old children (P less than 0.05). Likewise Hb displayed a gradual increase with age (P less than 0.001); the arithmetic mean Hb was 129 g/l in 4-year-old, 137 g/l in 8-year-old, and 143 g/l in 13-year-old children. Depleted iron stores (i.e. S-ferritin less than 12 micrograms/l) were present in 21.5% of 4-year-old, and in 12.7% of 8 and 13-year-old children. Latent iron deficiency (i.e. S-ferritin less than 10 micrograms/l and transferrin saturation less than 10%) was found in 3.1% of 4-year-old and in 0.5% of 8 to 13-year-old children. None of the children had iron deficiency anaemia. A high dietary intake of animal protein probably explains the low prevalence of iron deficiency.

Adolescent↗
PubMed1984

Serum iron, serum transferrin and transferrin saturation in healthy children without iron deficiency.

Serum iron, serum transferrin and transferrin saturation were studied in 253 healthy, non-anaemic children 4, 8 and 13 years old, and in 60 healthy, non-anaemic adults having serum ferritin values greater than or equal to 15 micrograms/l. One hundred and ninety-six children had serum ferritin values greater than or equal to 15 micrograms/l (i.e. replete iron stores), 35 had intermediate ferritin values from 10-14 micrograms/l and 22 had ferritin values less than 10 micrograms/l (i.e. depleted iron stores). Iron replete children showed a gradual rise in serum iron and transferrin saturation values with age. Serum iron and transferrin saturation values were lower (P less than 0.001, P less than 0.0001) and transferrin values higher (P less than 0.0001) in iron replete children compared to adults. Iron replete children had a 2.5 centile transferrin saturation value of 5%; 19.9% of these children had saturation values less than 15% and 8.2% had values less than 10%. In iron depleted children a transferrin saturation value less than 7% yielded the highest diagnostic efficiency as regards exhausted iron stores, although with a low predictive value of a positive test. The transferrin saturation is unsuitable as a single diagnostic criterion in the evaluation of iron deficiency in children and should always be combined with other indicators of iron status.

Adolescent↗
PubMed1984

Quantitative analysis of wide-field endothelial specular photomicrographs.

Samples from the center of a wide-field specular micrograph adequately assessed cell density and frequency distribution of cell areas. A preliminary analysis of the spread of values indicated whether an increased sample size was required. An algorithm determined how large a sample taken from the central photograph (three, five, or nine rectangles) was necessary to permit detection of a 10% change in cell area. This analysis of sample size also indicated that sampling by small-field specular microscopy was not representative of the surrounding square millimeter of corneal endothelium.

Cell Count↗
PubMed1984

Specular microscopy of hard contact lens wearers.

Wide-field specular microscopy, slit-lamp examination, and pachometry were performed on 22 successful hard contact lens wearers and 22 controls matched for age, race, sex, and refractive error. A minimum of 600 cells per control and 1200 per contact lens wearer were manually digitized from the specular photomicrographs. Frequency distributions of cell areas were compared between the two groups using the parameters of mean, median, standard deviation, coefficient of variation, skewness and kurtosis. Slit-lamp examination was normal and there was no significant difference in corneal thickness between the patient group and the control group. Comparison of mean, median, and standard deviation also revealed no significant difference, but skewness (P less than .001), kurtosis (P less than .001) and coefficient of variation (P less than .004) were greater in the hard contact lens wear group. Hard contact lens wearing time correlated with increasing pleomorphism (P less than .05). Specular microscopy also revealed morphologic changes including deep stromal striae, intra- and extracellular "blackout" areas, and clustering of extremely small and large cells. The possible relationship between endothelial hypoxia and structural stromal changes are discussed.

Adult↗
PubMed1983

Antibodies to herpes simplex and Epstein-Barr viruses in Faroese children: association with sibship size, height and age.

Antibody to herpes simplex virus (HSV) type 1 and Epstein-Barr virus (EBV) capsid antibody were determined in 333 children from the Faroe Islands, aged 4, 8 and 13 years. An analysis of multi-way frequency tables was performed, testing seropositivity for each virus against combinations of the following variables: sibship size, birth order, mother's age at birth, birth weight, actual height and weight, age and sex. HSV-seropositivity was associated to sibship size, height and age, while EBV-seropositivity was related only to age.--It is discussed how the findings fit into epidemiological patterns described for Hodgkin's disease and multiple sclerosis, which are both supposed to be of viral origin. Our results suggest that HSV, but not EBV, may be among the candidates to be considered.

Adolescent↗