PubMed Health⌕ Search

Biomedical subjects

D Levin

Publications and source records attributed to D Levin.

At least 55 records · Page 3Linked to original sources
PubMed1989

AIDS-related secular trends in cancer in Los Angeles County men: a comparison by marital status.

Data from the population-based cancer registry for Los Angeles County, an area with high risk of AIDS, were used to evaluate secular trends of Kaposi's sarcoma (KS), non-Hodgkin's lymphoma, and other possibly AIDS-related cancers in men aged 18 to 54. Marital status was used as a surrogate for homosexual behavior to compare the proportional incidence rates for the pre-AIDS era, 1972 to 1979, to those for 1980 to 1982 and 1983 to 1985. Both absolute incidence and proportional incidence of KS continue to increase sharply, although in absolute numbers, KS is making a smaller contribution to the total number of AIDS cases as the Los Angeles County epidemic progresses. For never-married men the proportional incidence rate of KS in 1983 to 1985 was nearly 100-fold greater than that of 1972 to 1979 and 7-fold greater than that of 1980 to 1982. High-grade lymphomas show statistically significant secular increases in both never-married and ever-married men, but only the rates of Burkitt's lymphomas have increased to a greater extent in never-married men. A small but significant increase of central nervous system lymphomas is seen in both marital status groups. There is no evidence of any AIDS-related increases in Hodgkin's disease, leukemia, testicular cancer, anal cancer, liver cancer, oral cancer, multiple myeloma, or malignant melanoma. As of 1985, cancer, as a manifestation of AIDS, is still apparently limited to KS and high-grade lymphomas (particularly Burkitt's) in Los Angeles County.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Interleukin production by neonatal spleen cells during and as a result of antigen presentation: the effect of ultraviolet light.

Antigen presentation by neonatal murine spleen cells and the production of lymphokines and interleukins involved in the stimulation of a T-helper-2 (TH2) cell line (D10-G4.1) were studied as were the effects of ultra violet (UV)-irradiation on this system. Neonatal spleen cells are less capable than adult cells of performing the initial steps of the immune response required for antigen dependent activation of TH2 cells. These steps include soluble antigen processing and presentation and as a result reduced production of IL-4 and IL-1-Inducer Factor ("IL-1-IF") by the T-helper cells and reduced production of IL-1 and IL-2 by the antigen presenting cell population. Spontaneous membrane IL-1 activity is low in the neonate, however, when exposed to "IL-1-IF" they can express adult levels. Ultra-violet (UV) irradiation of the antigen presenting population has a damaging effect on all the above mentioned processes. Antigen processing and presentation, induction of D10 IL-4 production and proliferation, and IL-2 production demonstrate two different age related patterns of UV-irradiation induced damage: a dose dependent inhibition when adult cells are irradiated and an inverse effect in which low doses of irradiation were more inhibitory than higher doses when neonatal cells are irradiated. However, the secretion and membrane expression of IL-1 by both age groups are directly and totally inhibited by the range of UV-irradiation doses used and cannot be reinduced with a supplement of a crude "IL-1-IF". While the capacity to produced IL-1 is totally destroyed by UV-irradiation, the ability to produce IL-2 remains intact and remains responsive to an "IL-2-Inducer" activity during proper antigen presentation. The low responses of neonatal antigen presenting spleen cell populations and the damaging effect of UV on both neonatal and adult responses are not due to the induction of suppressor factors.

Animals↗
PubMed1988

IL-1 secretion and membrane IL-1 expression by neonatal spleen cells during soluble antigen presentation.

Antigen presentation and IL-1 production by neonatal spleen cells were studied in a murine model. The T-helper-cell line (D10-G4.1) (D10), which is specific for soluble antigen presented on syngeneic antigen-presenting cells and dependent on IL-1 for its proliferation, was used as an indicator cell for the ability of syngeneic neonatal or adult spleen cells to present antigen and produce IL-1. The antigen-presenting capacity of neonatal spleen cells is low as attested by D10 proliferation. During antigen presentation there is an augmentation of IL-1 production by the antigen-presenting spleen cell population. However, neonatal spleen cells do not respond to the same levels as do adult spleen cells. These reduced levels of secreted IL-1 cannot be attributed to a low potential for producing IL-1 as attested by the high levels of IL-1 made by these cells after induction by a crude IL-1 inducer factor (IL-1-IF) and by the stimulus of the IL-1-IF produced by D10 cells during antigen presentation by paraformaldehyde-fixed adult cells. The spontaneous expression of membrane IL-1 by neonatal cells is low. Membrane IL-1 levels on neonatal cells can be brought to adult levels by induction with IL-1-IF. Neonatal spleen cells have an impaired capacity to process and/or present soluble antigen. This impairment leads to a decreased stimulus of the T helper cell to produce inducer factors and thus a reduced level of IL-1 production by the neonatal cells during antigen presentation.

Age Factors↗
PubMed1988

Reflex effect of skeletal muscle mechanoreceptor stimulation on the cardiovascular system.

To determine the potential for mechanical stimulation of skeletal muscle to contribute to the reflex cardiovascular response to static contraction (exercise reflex), we examined the cardiovascular effects caused by either passive stretch or external pressure applied to the triceps surae muscles. First, the triceps surae were stretched to an average developed tension of 4.8 +/- 0.3 kg. This resulted in increases in mean arterial pressure (MAP) of 28 +/- 7 mmHg, dP/dt of 1,060 +/- 676 mmHg/s, and heart rate (HR) of 6 +/- 2 beats/min (P less than 0.05). Additionally, increments of 0.3, 0.5, 1.0, 2.0, 4.0, and 8.0 kg of tension produced by passive stretch elicited pressor responses of -6 +/- 1, 7 +/- 1, 16 +/- 3, 21 +/- 8, 28 +/- 6, and 54 +/- 9 mmHg, respectively. External pressure, applied with a cuff to the triceps surae to produce intramuscular pressures (125-300 mmHg) that were similar to those seen during static contraction, also elicited small increases in MAP (4 +/- 1 to 10 +/- 1 mmHg) but did not alter HR. Transection of dorsal roots L5-L7 and S1 abolished the responses to passive stretch and external pressure. Moreover, when the triceps surae were stretched passively to produce a pattern and amount of tension similar to that seen during static hindlimb contraction, a significant reflex cardiovascular response occurred. During this maneuver, the pressor response averaged 51% of that seen during contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1986

Pneumocystis carinii pneumonia with spontaneous pneumothorax. A report of three cases.

Spontaneous pneumothorax is a rare complication of pneumonia. Three cases of spontaneous pneumothorax in patients with Pneumocystis carinii pneumonia and acquired immunodeficiency syndrome are described. Two patients had bronchopleural fistulas. Local subpleural necrosis was felt to be the cause of the pneumothorax. Pneumothorax should be considered in patients with P carinii pneumonia who experience respiratory deterioration.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Poliovirus replicase stimulation by terminal uridylyl transferase.

In an in vitro poliovirus replication system, purified viral polymerase, plus sense virion RNA, and a host factor have been previously shown to be necessary for the transcription of minus strands. We have found that a partially purified eukaryotic initiation factor-2 (eIF-2) fraction from rabbit reticulocytes can replace HeLa host factor in the replicase reaction. This enzyme preparation contains eIF-2 and two other major proteins. In addition to eIF-2 activity, which does not appear to play a role in the replicase reaction, we find that the fraction contains terminal uridylyl transferase activity. The enzyme adds UMP moieties to the 3' end of primer RNA molecules. The number of UMP residues added depends on the primer. Although long tails of heterogeneous lengths (50 to 100 nucleotides) can be polymerized on the 3' end of oligo(U), a poly(A) primer accepts only four U's. The terminal uridylyl transferase activity requires only UTP, Mg2+, a sulfhydryl reagent, and an RNA primer for activity. It is partially associated with ribosomes. We provide preliminary evidence that it may be responsible for host factor-like activity. We present a model for minus strand synthesis by poliovirus replicase, based on the hypothesis that a terminal uridylyl transferase can participate in initiation.

Base Sequence↗
PubMed1984

The diffusing capacity as a predictor of arterial oxygen desaturation during exercise in patients with chronic obstructive pulmonary disease.

We evaluated 48 patients with chronic obstructive pulmonary disease by means of pulmonary-function and exercise testing to determine whether any tests of pulmonary function could predict the development of arterial desaturation during exercise. We found that only two indexes--diffusing capacity and forced expiratory volume in one second (FEV1)--were predictive of desaturation. The diffusing capacity was more specific and sensitive than FEV1. A diffusing capacity above 55 per cent of predicted was 100 per cent specific in excluding desaturation, as compared with an 82 per cent specificity for an FEV1 above 55 per cent of predicted. With this cutoff point, the sensitivity of the diffusing capacity was 68 per cent, as compared with 46 per cent for the FEV1. Both the frequency and the magnitude of arterial desaturation increased substantially when the diffusing capacity was below 55 per cent of predicted. Testing the diffusing capacity should be useful in identifying which patients with chronic obstructive lung disease are likely to become desaturated during exercise and may therefore benefit from oxygen therapy.

Aged↗
PubMed1984

Antiepileptic effects of amphetamine may require GABA (benzodiazepine) activity.

Secondary components of visual evoked potentials (slow negative wave-SNW, and photically-evoked sensory after discharge-SAD) are known to be precursors of experimentally activated wave-spike discharges, similar to wave-spikes of petit mal epilepsy. Both SNW and SAD may be potently suppressed either by amphetamine or GABAergic compounds such as diazepam and sodium valproate. A hypothesis was tested in the present study, that amphetamine-induced suppression of wave-spike discharges may require GABA-benzodiazepine activity for its expression. Electrocortical activity was recorded and averaged in unrestrained albino rats with chronically implanted epicortical electrodes. SNW and SAD obtained in habituated rats in the predrug state were potently suppressed by amphetamine (1 mg/kg, i.p.). Fifteen minutes after amphetamine injection, a challenging drug (metrazol, picrotoxin, convulsant benzodiazepine, Ro 5-3663, or imidazodiazepine, Ro 15-1788) was administered intraperitoneally. Subconvulsive doses of metrazol (10 mg/kg) reversed amphetamine suppression; imidazodiazepine (20 mg/kg) and picrotoxin (1.5 mg/kg) reliably opposed the SNW suppression; convulsant benzodiazepine, Ro 5-3663 (2 mg/kg), showed modest and nonsignificant effect in the same direction. It is proposed that the antiepileptic potency of amphetamine may be associated with its ability, apparently via modulatory effect of norepinephrine, to facilitate the activation of benzodiazepine-GABA receptors.

Amphetamine↗
PubMed1984

Control of protein synthesis in human reticulocytes by heme-regulated and double-stranded RNA dependent eIF-2 alpha kinases.

Heme-deficiency and double-stranded RNA (dsRNA) activate distinct cyclic 3':5'-AMP independent protein kinases (HRI and dsI, respectively) in rabbit reticulocyte lysates. These kinases inhibit protein synthesis by phosphorylating the 38,000 daltons (38K) subunit of the initiation factor eIF-2 (eIF-2 alpha). Using separation techniques to obtain a reticulocyte enriched fraction and reticulocyte-free erythrocytes, we have prepared lysates of these fractions from normal human whole blood. Human reticulocyte-enriched lysates contain the hemin-regulated and dsRNA-dependent protein kinases which inhibit protein synthesis and which phosphorylate rabbit eIF-2 alpha. An endogenous 38K polypeptide which co-migrates with rabbit eIF-2 alpha is also phosphorylated. In contrast, human mature erythrocytes contain little or no heme-regulated or dsRNA-dependent eIF-2 alpha kinase activities which are inhibitory of protein synthesis.

Blood Proteins↗
PubMed1984

Visual evoked potentials and nociceptive thresholds in high and low self-stimulators.

Tail flick latencies (TFL) were examined in order to distinguish between rats from genetically high (HI) and low (LO) self-stimulation lines (LC2-HI and LC2-LO). In addition, slow secondary negative wave (SNW) of the visual evoked potential, which is considered to be a sensitive index of normal and pharmacologically-induced behavioral arousal, was analysed. Small, albeit statistically significant enhancement of SNW was obtained in LO rats. Unlike LO animals, HI rats gained in SNW amplitude during repeated photic stimulation. The difference between the lines was highly significant. TFL assessment yielded slightly reduced (NS) values for HI rats. However, when TFL and SNW data were compared it appeared that TFL vary as a function of SNW amplitude in LO but not in HI rats, (r = 0.9). SNW may be employed as a predictor of the nociceptive threshold in rats.

Animals↗
PubMed1984

Visual evoked potentials in rats selected for high or low self-stimulation.

Visual evoked potentials (VEPs) were analyzed in order to distinguish between rats from genetically high (HI) and low (LO) self-stimulation lines (LC2-HI and LC2-LO). Secondary VEP components - slow secondary negative wave (SNW) and sensory afterdischarge (SAD) - which are considered to be most sensitive indices of normal and pharmacologically-induced behavioral changes, were used for the comparison. Small, albeit statistically significant enhancement of SNW and SAD was obtained in LO rats. Unlike LO animals, HI rats gained in SNW amplitude and SAD area during repeated photic stimulation. The difference being highly significant. D,L-Amphetamine (1 mg/kg, i.p.) suppressed SAD and reduced the SNW amplitude in both HI and LO animals, although the predrug difference in their values remained practically unaltered. Apomorphine (0.25, 2.75, 5.25 mg/kg i.p.) had no measurable effect on VEP parameters even though it caused a regular picture of dose-related enhancement of locomotion and stereotypy. The effect of amphetamine can, therefore, be attributed to the activation of the norepinephrinergic system. Correspondingly, VEP variance in the two lines of rats is interpreted as related to the peculiarities of norepinephrine modulation of neocortical activity.

Amphetamine↗
PubMed1984

MMPI differences among mild and severe insomniacs and good sleepers.

Past research has attempted to delineate personality differences between insomniacs and good sleepers but has failed to control for type of insomnia or severity of the disorder. The purpose of this study was to compare MMPI scores of mild and severe sleep onset insomniacs with a control group of noninsomniacs . Results demonstrated that sleep onset insomniacs, regardless of degree of severity, differed significantly from noninsomniacs ; and that mild and severe insomniacs differed from each other on only one MMPI scale.

Adolescent↗