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Biomedical subjects

J M Novak

Publications and source records attributed to J M Novak.

29 records · Page 2Linked to original sources
PubMed1988

Effect of hypo-osmotic incubation on membrane recycling.

Incubation of alveolar macrophages in hypo-osmotic media causes a time-and temperature-dependent increase in the number of surface receptors for three different ligands. Exposure of cells to solutions of 210 mOsM or less, at 37 degrees C but not at 0 degree C, resulted in an increase in the number of surface receptors for diferric transferrin, alpha-macroglobulin-protease complexes, and mannose-terminated glycoproteins. Upon media dilution at 37 degrees C, surface receptor number reached a maximum within 5 min and returned to near-normal values by 30 min. The increase in surface receptor number was the result of a decrease in the rate of internalization of receptors, either occupied or unoccupied. The rate of receptor exteriorization was unaltered by hypo-osmotic incubation of cells. The rate of fluid-phase pinocytosis was also inhibited upon incubation in hypo-osmotic solution. In experiments in which both receptor-mediated endocytosis and fluid phase pinocytosis were measured on the same samples, inhibition of both processes occurred with the same kinetics and to a similar extent. The rate of receptor-mediated endocytosis recovered to normal rates after 60 min in hypo-osmotic solutions, whereas the rate of fluid phase pinocytosis did not recover to the same extent.

Animals↗
PubMed1988

Regulatory volume decrease in alveolar macrophages: cation loss is not correlated with changes in membrane recycling.

Alveolar macrophages regain their normal volume after swelling in hypo-osmotic solutions. This process, termed regulatory volume decrease (RVD), is initiated 3-5 minutes after exposure of cells to hypo-osmotic solutions, and by 30 min, near-normal volumes are attained. Volume decrease does not occur at 0 degrees C or in solutions in which Na+ has been replaced by K+, or Cl- by the impermeant anion gluconate. These results, as well as direct measurement of intracellular cations, indicate that decreases in cell volume result primarily from the loss of K+ and Cl- and are similar to RVD in lymphocytes. Kinetic analysis of cation loss, both by directly measuring changes in intracellular cation content and by assaying rubidium efflux, showed that cation loss occurred immediately upon media dilution. The rate of cation loss fit first-order kinetics and preceded both the initiation of volume decrease and the maximum increase in surface receptor number. These results suggest that the cation transporters responsible for RVD are located at the cell surface and that regulation of activity is not dependent on alterations in membrane movement.

Animals↗
PubMed1987

Optic nerve hypoplasia.

Optic nerve hypoplasia is now recognized as a common developmental anomaly of the optic nerve. It has a large clinical spectrum of findings, but is most often associated with impaired vision and a small optic disc. Additional findings which aid in the diagnosis include a Marcus Gunn pupil, a double peripapillary ring, and pathological thinness of the retinal nerve fiber layer. Bilateral optic nerve hypoplasia may be a clue to midline developmental anomalies of the brain. Our case of optic nerve hypoplasia illustrates its variability of presentation and underscores the importance in investigating every case of unexplained decreased vision.

Diagnosis, Differential↗
PubMed1984

Current status of Credé prophylaxis.

The time-honored practice of silver nitrate application to the eyes of newborns is compared to the use of antibiotics. Side effects, effectiveness, and clinical practicality in preventing ophthalmia neonatorum are considered. The inability of prophylactic agents to inhibit several serious pathogens that cause conjunctivitis of the newborn is a factor. Prenatal screening for venereal disease and close observation of the baby's eyes in the postpartum period are additional ways to decrease the incidence of ophthalmia neonatorum.

Anti-Bacterial Agents↗
PubMed1983

Medial septal lesions, radial arm maze performance, and sympathetic sprouting: a study of recovery of function.

Long-Evans rats received septal lesions or sham operations and were tested for performance in a radial arm maze, level of activity and water intake in order to test whether recovery of function was mediated by sprouting of peripheral sympathetic fibers. Animals receiving septal lesions displayed an initial deficit in radial arm maze performance followed by recovery. No critical changes occurred in activity level and no recovery was seen in water intake. Subsequent superior cervical ganglionectomies had no effect on recovery of radial arm maze performance. There was a significant relationship between behavioral recovery and the degree of hippocampal AChE depletion. It is concluded that recovery of radial arm maze performance is not mediated by sympathetic sprouting following septal lesions but might be mediated by residual septohippocampal fibers.

Acetylcholine↗
PubMed1983

Phencyclidine and behavior: II. Active avoidance learning and radial arm maze performance.

Rats with injections of 4 or 8 mg/kg of phencyclidine (PCP) are impaired in the acquisition of active avoidance learning and radial arm maze performance. This impairment was not due to a change in detectability of aversive stimuli or the inability to perform the correct response. The primary deficit appears to be the inability of PCP injected animals to encode the appropriate attributes (e.g., environmental context, response selection, and emotion) associated with each task.

Animals↗
PubMed1983

Episodic long-term memory in the rat: effects of hippocampal stimulation.

Rats with electrodes implanted in dorsal hippocampus were trained to perform a delayed spatial matching-to-sample task on a radial arm maze. Subseizure level electrical stimulation of the dorsal hippocampus applied during the study phase disrupted retention of a specific arm when tested at a 20-min delay but had no effects at 1- and 12-min delays. There were no state-dependent or proactive effects of stimulation. Subseizure level stimulation of the hippocampus immediately after the study phase resulted in normal retention. In contrast, seizure level stimulation of the hippocampus applied either during or immediately after the study phase disrupted retention at all three (1, 12, 20 min) retention delays. The data support the interpretation that the hippocampus is involved in the encoding of critical information (spatiotemporal attributes) in long-term working memory, but not short-term memory.

Animals↗
PubMed1982

Serial position curve in rats: role of the dorsal hippocampus.

In an eight-arm radial maze, normal rats demonstrated good immediate retention for the order of first items (primacy component of serial position curve) and last items (recency component of serial position curve) of an eight-item (arm) list. In contrast, rats with dorsal hippocampal lesions displayed, on an immediate retention test, disruption of the primacy but not the recency component of the serial position curve. Furthermore, imposing a 10-minute delay before the retention test impaired all components of the serial position curve. These results support correspondence in mnemonic function of the hippocampus in animals and humans.

Animals↗
PubMed1979

Effects of radiation on the human gastrointestinal tract.

Radiation therapy directed at the abdomen may damage the digestive tract, the type and extent of injury depending on the dose of the radiation and the radiation sensitivity of the gut. Characteristic early changes are manifest in the mucosa of the gut: for later ulceration, changes in the collagen tissues and particularly in the vascular channels occur. This paper describes and characterizes injuries to the esophagus, stomach, small intestine and colon. It emphasizes the importance of recognizing radiation-induced damage to the gut which may occur early or late after radiation.

Adult↗
PubMedDate not supplied

Dissolved phosphorus retention and release from a coastal plain in-stream wetland.

Dissolved phosphorus (DP) can be released from wetlands as a result of flooding or shifts in water column concentrations. Our objectives were to determine the long-term (1460 d) DP retention and release characteristics of an in-stream wetland, and to evaluate how these characteristics respond to flooding, draining, and changes in DP concentrations. The studied in-stream wetland drains an agriculturally intensive subwatershed in the North Carolina Coastal Plain region. The wetland's DP retention and release characteristics were evaluated by measuring inflow and outflow DP concentrations, DP mass balance, and DP movement across the sediment-water column interface. Phosphorus sorption isotherms were measured to determine the sediment's equilibria P concentration (EPCo), and passive samplers were used to measure sediment pore water DP concentrations. Initially, the in-stream wetland was undersized (0.31 ha) and released 1.5 kg of DP. Increasing the in-stream wetland area to 0.67 ha by flooding resulted in more DP retention (28 kg) and low outflow DP concentrations. Draining the in-stream wetland from 0.67 to 0.33 ha caused the release of stored DP (12.1 kg). Shifts both in sediment pore water DP concentrations and sediment EPCo values corroborate the release of stored DP. Reflooding the wetland from 0.33 to 0.85 ha caused additional release of stored DP into the outflowing stream (10.9 kg). We conclude that for a time period, this in-stream wetland did provide DP retention. During other time periods, DP was released due to changes in wetland area, rainfall, and DP concentrations.

Fresh Water↗