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Biomedical subjects

D H Schwartz

Publications and source records attributed to D H Schwartz.

16 recordsLinked to original sources
PubMed1992

Decrease in HIV provirus in peripheral blood mononuclear cells during zidovudine and human rIL-2 administration.

Quantification of human immunodeficiency virus (HIV) proviral DNA in peripheral blood mononuclear cells (PBMC) was performed in 13 HIV-seropositive asymptomatic individuals during 10-24 months by polymerase chain reaction amplification of multiple half-log dilutions of cellular DNA. At enrollment, subjects had a geometric mean titer of 100 copies of HIV provirus per 10(6) PBMC (mean +/- SD, 2 +/- 0.9 log10). In four untreated individuals there was no significant change in provirus levels during a mean period of 13.3 months. In eight patients treated with zidovudine (ZDV) and human recombinant interleukin 2 (rIL-2), HIV provirus copies declined to 13 per 10(6) cells (1.1 +/- 0.8 log10) at the end of the first course of ZDV and rIL-2 at week 20 (p less than 0.01), and to 40 per 10(6) cells (1.6 +/- 0.9 log10) after 12 months of treatment (p less than 0.04). Subsequent courses, which included 12 weeks of ZDV alone or 4 weeks of IL-2 alone, did not significantly change the already depressed provirus copy numbers. Proviral copy number also remained depressed during drug-free "washout periods" between courses. Finally, we observed a return to a geometric mean of 400 copies per 10(6) cells (2.6 +/- 0.3 log10) a mean of 7.9 months after discontinuation of therapy. Measurement of changes in HIV provirus should provide a direct marker for defining antiviral activity of drugs, biologics, and combination therapy.

DNA, Viral↗
PubMed1991

Antibody responses to Haemophilus influenzae type B vaccines in men with human immunodeficiency virus infection.

BACKGROUND: Persons with human immunodeficiency virus (HIV) infection are at increased risk for serious infections caused by Haemophilus influenzae, yet there are few data on their antibody responses to the H. influenzae type b vaccines. METHODS: We evaluated antibody responses in 248 men who were randomly assigned to receive a single dose of either the H. influenzae type b polysaccharide (PRP) vaccine or the polysaccharide-mutant diphtheria toxoid conjugate vaccine (PRP-CRM). The subjects were stratified into four groups: seronegative men (67 subjects), men with asymptomatic HIV infection (79), men with symptomatic HIV infection (47), and men with the acquired immunodeficiency syndrome (AIDS) (55). RESULTS: Before immunization, the subjects with AIDS had the lowest PRP-antibody titers; 40 percent had titers below the putative protective level (less than 0.15 micrograms per milliliter). In the seronegative subjects, those with asymptomatic HIV infection, and those with symptomatic HIV infection, the PRP-CRM vaccine led to a threefold greater increase in geometric mean antibody titers than did the PRP vaccine (P less than 0.01). However, the subjects with AIDS had a greater antibody response to the PRP vaccine. The antibody response of HIV-seropositive men to the PRP-CRM vaccine correlated significantly with the number of CD4 lymphocytes (r = 0.47, P less than 0.0001, as compared with r = -0.01 for the PRP vaccine). In these HIV-infected men, both vaccines elicited the dominant anti-PRP idiotype described previously in populations not infected with HIV. CONCLUSIONS: Immunization with the PRP-CRM conjugate vaccine early in the course of HIV infection is likely to confer protection against disease caused by H. influenzae type b.

AIDS Vaccines↗
PubMed1991

Stimulus-evoked changes in neostriatal dopamine levels in awake and anesthetized rats as measured by microdialysis.

The effect of medial forebrain bundle (MFB) stimulation on neostriatal dopamine levels was examined using in vivo microdialysis in urethane-anesthetized and awake, freely-moving rats in conjunction with single unit extracellular recordings from antidromically identified nigral dopaminergic neurons. Dialysis samples were collected during baseline periods or while stimulating the MFB with trains of 5 or 10 pulses at different frequencies within a physiologically relevant range. When the perfusion solution contained 1.2 mM Ca2+, even intense, high frequency stimulation was ineffective at producing significant elevations in neostriatal dopamine levels whereas cocaine or amphetamine reliably caused several-fold elevations in dopamine levels. When the perfusate contained 2.4 mM Ca2+, modest MFB stimulation within the range of spontaneous nigral cell firing produced large and reliable increases in dopamine levels. There was a significant correlation between the proportion of dopaminergic neurons that could be antidromically activated from the MFB and the increase in neostriatal dopamine. There was no effect of stimulus pattern on the increase in dopamine levels, and results obtained in awake, freely-moving animals did not differ from those obtained in anesthetized animals. These data provide good evidence that in vivo microdialysis is sensitive to neostriatal dopamine overflow evoked by stimulation within the normal rate of firing of nigrostriatal neurons and that Ringer's Ca2+ concentration is a critical variable in the detection of stimulus-induced release of dopamine.

Anesthesia↗
PubMed1991

Detection and quantification of human immunodeficiency virus RNA in patient serum by use of the polymerase chain reaction.

Human immunodeficiency virus (HIV) RNA was detected and quantified in the serum of HIV-seropositive individuals using the polymerase chain reaction (PCR) and a nonisotopic enzyme-linked affinity assay. Of 55 HIV-infected patients who were not receiving therapy, serum HIV RNA was detected in 9 of 19 who were asymptomatic, 11 of 16 with AIDS-related complex (ARC), and 18 of 20 with AIDS, with copy numbers ranging from 10(2) to greater than or equal to 5 x 10(4) 200 microliters of serum based on a relationship between absorbance and known copy number of gag gene RNA. Linear regression analysis demonstrated a correlation between infectious titer in 42 patient sera cocultured with donor peripheral blood mononuclear cells (PBMC) and PCR product absorbance (r = .70, P less than .01). Serum HIV RNA detected by PCR also correlated with serum p24 antigen positivity, CD4 counts less than 400/mm3, and the presence of HIV-related symptoms or disease. Quantification of infectious HIV RNA in cell-free serum by PCR may be useful as a marker for for disease progression or in monitoring antiviral therapy.

AIDS-Related Complex↗
PubMed1991

Absent or rare human immunodeficiency virus infection of bone marrow stem/progenitor cells in vivo.

An important question in human immunodeficiency virus (HIV) pathogenesis is whether HIV-infected bone marrow CD34+ stem/progenitor cells serve as a significant reservoir of virus in HIV-infected individuals. Our data indicate that infection of bone marrow stem/progenitor cells with HIV occurs rarely, if ever, in vivo. In the present study, CD34+ cells were immunomagnetically purified from the bone marrow of HIV-seropositive individuals, and purified cells or colony-forming cells of the granulocyte/macrophage lineage were analyzed for HIV proviral DNA by the polymerase chain reaction. No HIV DNA was detected in colony-forming cells of the granulocyte/macrophage lineage from HIV-positive patients. Furthermore, no virus was found in CD34(+)-enriched cells from six of seven samples from asymptomatic HIV-infected individuals and four of four samples from patients with AIDS-related complex or AIDS. Thus, infected stem cells are not a major source of persistent HIV and do not account for hematopoietic suppression. These findings have positive implications for the concept of marrow reconstitution with autologous stem cells, genetically engineered for HIV resistance, following marrow-ablative antiviral therapy.

DNA, Viral↗
PubMed1991

Safety and effects of interleukin-2 plus zidovudine in asymptomatic individuals infected with human immunodeficiency virus.

The safety of continuous i.v. interleukin-2 (IL-2) in conjunction with zidovudine (ZDV) was assessed in asymptomatic patients infected with human immunodeficiency virus. Clinical, immunologic, and viral parameters were monitored in a phase I/II trial with dose escalation and crossover arms. Daily doses of IL-2 from 1.5 to 12 x 10(6) IU/m2 were well tolerated and, in the presence of ZDV, did not induce increases in p24 antigenemia. Significant (p less than 0.05) but transient increases in CD4 cells were observed midway through infusion of IL-2 at all doses, and increases in natural and lymphokine-activated killer activity were seen at higher doses. Circulating hypodense eosinophils and soluble IL-2 receptors increased more than 10-fold. Of nine patients available for long-term follow up 13-25 months from baseline and 4-21 months after stopping IL-2, six still had improved CD4 counts (versus baseline), and the mean increase (135/mm3) for all nine patients was significant (p less than 0.05). Eight of these nine patients were negative for serum p24 at the start of therapy, and none had become p24 antigenemic at long-term follow-up.

Adult↗
PubMed1990

Serotonin release in lateral and medial hypothalamus during feeding and its anticipation.

In the present experiments we extend previous findings that established a relationship between feeding behavior and hypothalamic serotonin as measured by in vivo microdialysis. The new result is hypothalamic release of serotonin in anticipation of eating when the animal sees and smells food. We have now verified brain serotonin peaks in four different ways: 1) a serotonergic reuptake blocker (fluoxetine 1 or 10 microM) in the perfusion medium raised basal levels of serotonin, 2) every sample was oxidized at two potentials using a dual potentiostat to confirm the voltage characteristics of each peak, 3) serotonin peaks were reduced by the selective serotonin cell body agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), thus helping confirm that most of the serotonin observed in these experiments was neuronal in origin, and 4) lateral and medial hypothalamic microdialysis probes were used simultaneously to monitor the degree of diffusion from one to the other. The results show that extracellular serotonin increases at both sites during preingestive events as well as during eating, but not afterwards.

Animals↗
PubMed1990

Tryptophan increases extracellular serotonin in the lateral hypothalamus of food-deprived rats.

Although it is well established that increases in tryptophan availability can increase brain serotonin synthesis, the effect of tryptophan loads on serotonin release is not as clear. We have used in vivo microdialysis in order to monitor extracellular serotonin in the lateral hypothalamus to examine this issue. Tryptophan methyl ester (100 mg/kg IP) was administered to ad lib-fed and 48-h food-deprived rats. The results suggest that a peripheral tryptophan load can elevate extracellular serotonin in food-deprived subjects more effectively than in food-replete subjects.

Animals↗
PubMed1989

Feeding increases extracellular serotonin in the lateral hypothalamus of the rat as measured by microdialysis.

Microdialysis probes inserted into chronically implanted guide shafts allowed the collection of serotonin and 5-hydroxyindoleacetic acid (5-HIAA) from the lateral hypothalamus of rats during feeding behavior. After the collection of baseline samples, animals were offered a palatable diet that they could only see and smell for 60 min, then they were allowed access to the food for an hour. An additional three samples were collected after food was removed. Extracellular serotonin increased during the first half hour of access when the animals actually ate the food, and then returned to baseline level throughout the remainder of the test. 5-HIAA decreased gradually with no increase during feeding. These data suggest that eating a meal of palatable food causes a short-term increase in extracellular serotonin in the lateral hypothalamus. This increased serotonin may play a role in the control of lateral hypothalamic feeding and reward.

Animals↗
PubMed1989

Patterns of extracellular norepinephrine in the paraventricular hypothalamus: relationship to circadian rhythm and deprivation-induced eating behavior.

In order to clarify the physiological role of norepinephrine (NE) in the hypothalamic paraventricular nucleus (PVN), changes in extracellular levels of endogenous NE were measured in 11 freely-moving rats using microdialysis and high pressure liquid chromatography with electrochemical detection. To determine whether there was a circadian pattern of extracellular NE in freely-eating subjects, samples of dialysate from the vicinity of the PVN were collected and assayed for NE every 2 hrs for 48 hrs. The pattern of NE averaged across subjects was similar during both 24-hr periods, with a reliable peak at the beginning of the dark cycle and relatively stable levels at all other times. When these animals were subsequently deprived of food for 24 hrs, a gradual rise in extracellular NE was observed, ultimately increasing to 215% of the predeprivation level. When the animals were refed and NE measurements were continued at more frequent intervals, extracellular levels were found to decline during the first 20 min of eating, as well as over the next 3 hrs as food intake diminished. These patterns of extracellular NE, together with previous evidence, suggest that endogenous NE in the PVN plays a role in the initiation and/or maintenance of normal eating behavior at the beginning of the nocturnal feeding period, as well as after food deprivation.

Animals↗
PubMed1989

Patterns of extracellular 5-hydroxyindoleacetic acid (5-HIAA) in the paraventricular hypothalamus (PVN): relation to circadian rhythm and deprivation-induced eating behavior.

Daily rhythms in extracellular levels of the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), were examined in the region of the paraventricular nucleus (PVN), using intracerebral microdialysis combined with high performance liquid chromatography and electrochemical detection. Samples of PVN dialysate, from 11 rats on a 12/12 hr light/dark cycle, were collected and assayed for 5-HIAA every 2 hr for 3 days. During the first 2 days the rats were given free access to food. During the 3rd day they were deprived of food for a 24-hr period and then given food for 4 hr. The results showed that in freely-feeding rats, there was a 24-hr rhythm in the levels of 5-HIAA, with a marked transient peak just after the beginning of the dark portion of the light/dark cycle and stable levels at all other times. When the animals were food-deprived, PVN levels of this metabolite remained stable, and the early dark peak was abolished, suggesting that it might have been consequent to the eating behavior which normally occurred at this time. In the 4-hr refeeding period, there were no changes in 5-HIAA levels, despite the intense eating behavior which occurred during this time. These patterns of 5-HIAA in the PVN region, taken together with previous evidence, suggest that PVN serotonin metabolism may increase in association with feeding specifically in the early portion of the nocturnal eating period, when it may play a role in controlling food intake and macronutrient selection.

Animals↗
PubMed1989

Microdialysis studies of brain norepinephrine, serotonin, and dopamine release during ingestive behavior. Theoretical and clinical implications.

This minireview deals with the possible roles of monoamines in feeding and feeding disorders. The introduction sketches the results of earlier studies with local drug injections and selective neurotoxins which provided pharmacological evidence that monoamines can influence food intake and body weight. A table summarizing this evidence is used to list monoamine changes that could underlie anorexia or hyperphagia. It is apparent that abnormalities in the monoamines, along with their cotransmitters, could cause many forms of feeding disorder. It is proposed as a working hypothesis that several varieties of hyperphagia leading to obesity have a common element. This common factor is a change in excitability of a lateral hypothalamic reinforcement system as manifested in self-stimulation at a stimulation-bound feeding site. Understanding this feeding reward-aversion system helps us understand hyperphagia and anorexia. The neurochemistry of reward and aversion involves the monoamines. This paper focuses on dopamine and serotonin. The data support the hypothesis that dopamine systems projecting to the nucleus accumbens and other forebrain areas from the mid-brain ventral tegmental area (VTA) are important for approach and positive reinforcement in ingestive behavior and self-stimulation. Serotonin is hypothesized to facilitate satiety and inhibition of feeding reward in the hypothalamus. The next section abstracts our recent experiments that measured pharmacological and physiological release of the monoamines in the hypothalamus and nucleus accumbens during ingestive behavior and self-stimulation. In vivo microdialysis in freely moving rats suggested the following: (1) Norepinephrine was released in the paraventricular nucleus during the active, feeding period of the circadian cycle. (2) The serotonin metabolite 5-HIAA also increased in the PVN at the same time if there was food to eat. (3) Amphetamine infused into the lateral hypothalamus (LH) by reverse dialysis increased synaptic dopamine, norepinephrine, and serotonin. (4) The anorectic drug d-fenfluramine increased synaptic serotonin in the LH and also increased the dopamine metabolite DOPAC, suggesting that serotonin and dopamine in the LH might contribute to fenfluramine-induced satiety. Local d-fenfluramine injection into the LH or local infusion by reverse dialysis again increased serotonin and decreased 5-HIAA and interfered with local dopamine metabolism as reflected in decreased DOPAC and HVA. (5) Tryptophan, a serotonin precursor, given systemically at an anorectic dose, increased extracellular serotonin in the LH, but this effect was only detectable in food-deprived rats. This was seemingly pH independent (between 5.8 and 8). The passage other cations through CFo is strictly suppressed (even at pH 8 and with 300 mM NaCl in the medium).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Effect of phenylpropanolamine on diet selection in rats.

Four doses of phenylpropanolamine (PPA; i.e., dl-norephedrine: 2.5, 5, 10, and 20 mg/kg) and saline were injected intraperitoneally in female rats maintained on a dietary self-selection paradigm. Intake of all three macronutrients (carbohydrate, fat, and protein) was equally affected by high doses of PPA. Lower doses decreased fat and protein more than carbohydrate.

Animals↗
PubMed1987

Requirement for mitogen, T cell-accessory cell contact, and interleukin 1 in the induction of resting T-cell proliferation.

The role of interleukin 1 (IL-1) and accessory cells (AC) in mitogen-driven, resting human peripheral blood T lymphocyte proliferation was examined utilizing highly purified T-cell preparations. Such preparations fail to respond to optimal concentrations of the lectin phytohemagglutin (PHA) or interleukin 2 (IL-2), indicating the functional depletion of monocytes (Mo.) and of activated T cells, respectively. The requirement for Mo. and IL-1 was quantitatively determined by adding known loads of Mo. and of recombinant human IL-1 alpha or beta forms (r-hIL-1, alpha/beta) to T-cell preparations and monitoring the resultant proliferative responses to the mitogens PHA, concanavalin A (Con A), the anti-CD3 monoclonal antibody (mAb) Leu 4, and Sepharose beads-linked Leu 4. Although some mitogens induced IL-2r gene transcription and surface expression in T cells, all mitogens tested failed to drive T cells to proliferate in the absence of Mo. r-h IL-1, as well as Mo.-conditioned media, failed to support the proliferation of mitogen-treated T cells. However, r-h IL-1 significantly amplified the proliferative responses of mitogen-treated T cells when suboptimal loads of Mo. were added. Both r-h IL-1 alpha and beta forms behaved identically in all the aforementioned experiments. The necessity of T cell-Mo. contact for T-cell proliferation was established by demonstrating that T cells separated from Mo. by a semipermeable membrane which allowed free diffusion macromolecules failed to proliferate to the mitogens tested. In contrast to lectins and anti-CD3 mAb phorbol-12-myristate-13-acetate (PMA) induced on its own a modest proliferative response which was greatly enhanced by r-h IL-1 independent of the addition of monocytes. The mechanism of r-h IL-1 action in supporting PMA-primed, T-cell proliferation involved the induction of IL-2 synthesis. We conclude that IL-1 does not substitute for the need for Mo. in supporting mitogen-driven T-cell proliferation. Mitogens, direct accessory-T-cell contact, and IL-1 each act, in this order, to bring about resting T-cell proliferation. The distinct behavior of PMA might relate to its ability to substitute for monocyte contact in promoting the progress of T cells through the cell cycle.

Antigen-Presenting Cells↗
PubMed1976

Societal responsibility for malpractice.

The purposes of providing just compensation to victims of medical injury and assuring high quality medical care are not served by the tort system. The tinkering with the tort system following the 1975 malpractice crisis will not ease the constantly increasing cost burden on the health care delivery system. Costs will double every three to four years. The only answer is a social insurance approach. The costs of a compensation system for medical injury regardless of fault could be met by eliminating the friction costs of the tort system, and would be helped by establishing national health insurance. The system could be initiated gradually and would be accompanied by quality assurance measures.

Attitude↗