Biomedical subjects

D Holtzman

Publications and source records attributed to D Holtzman.

At least 73 records · Page 4Linked to original sources

PubMed1989

Octanoic acid inhibits astrocyte volume control: implications for cerebral edema in Reye's syndrome.

Octanoic acid has been implicated in the pathogenesis of cytotoxic cerebral edema in Reye's syndrome. Using astrocytes from primary culture, we studied the dose-dependent effects of octanoate on cellular volume regulation and metabolism. Astrocyte volume recovery following hypoosmotic swelling was stimulated by 1.0 mM octanoate and inhibited by 3.0 mM octanoate. Parallel effects were obtained at these concentrations on the activity of the Na+,K+-dependent ATPase. Cellular ATP concentrations also were reduced 36% with the higher octanoate concentration. These effects of octanoate may contribute to the severe astrocyte swelling observed in the brains of Reye's syndrome patients.

Adenosine Triphosphate↗

PubMed1989

Cerebral oxygenation and blood flow in infant and young adult rats.

In vitro cerebral oxidative metabolism undergoes dramatic increases in infant rats between 10 and 20 days of age. To determine this was also the case in vivo, comparisons were made of cerebral blood flow (CBF) and oxygenation in rats at 10, 20, and 60-90 days of age, under pentobarbital sodium anesthesia. Measurements were made of CBF, arterial and venous O2 content, cerebral PO2 distributions, and the oxidation state of cytochrome-c oxidase (cytochrome aa3). CBF, O2 delivery, and O2 consumption all increased progressively with maturation. In contrast, cerebral PO2, cytochrome aa3 oxidation state, and O2 extraction fraction were higher in 20-day-old rats than in either 10-day-old or adult rats. We attribute this difference primarily to the high density of cerebral capillaries in the 20-day-old rat. We conclude that cerebral tissue PO2 and the oxidation state of cytochrome aa3 are determined by the density of perfused capillaries in addition to the more commonly accepted factors of cerebral O2 delivery and consumption.

Animals↗

PubMed1989

Tuberculosis and acquired immunodeficiency syndrome--Florida.

Florida reported 1858 cases of the acquired immunodeficiency syndrome (AIDS) and 8455 cases of tuberculosis from January 1, 1981, through October 31, 1986. Of the patients with AIDS, 159 (8.6%) also had tuberculosis, and 154 (1.8%) of the patients with tuberculosis also had AIDS. Among patients with both diagnoses, tuberculosis was diagnosed before AIDS by more than 1 month in 50%, was diagnosed within 1 month before or 1 month after the diagnosis of AIDS in 30%, and was diagnosed more than 1 month after the AIDS diagnosis in 20%. Compared with patients with AIDS only, patients with both diagnoses were also more likely to be Haitian, black (other than Haitian), or Hispanic. Compared with patients with tuberculosis only, patients with both diagnoses were more likely to be younger, male, Haitian, black (other than Haitian), and Hispanic, have extrapulmonary tuberculosis and negative tuberculin skin tests, and have noncavitary chest roentgenograms. These data suggest that patients with AIDS may have an increased risk of tuberculosis and that patients with both diagnoses differ in important demographic and clinical characteristics from patients with AIDS only or tuberculosis only.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Lead toxicity in primary cultured cerebral astrocytes and cerebellar granular neurons.

Neurons are more sensitive than astrocytes to lead toxicity in vivo. In order to understand the bases for the differences in brain cell responses to lead, the effects of lead acetate on cell morphology and on aerobic energy metabolism were studied in rat primary cultured neurons and astrocytes. By transmission electron microscopy, neuronal cell damage was seen with exposure to lead concentrations which were much lower than those required for similar changes in the astrocyte. As previously described in our studies of in vivo lead exposure, astrocytes in primary culture concentrated lead in nuclear, cytoplasmic, and lysosomal inclusions while neurons showed lead densities only in lysosomes. With acute lead exposures, inhibition of maximal respiratory capacity was greater and occurred at lower lead concentrations in neurons than in astrocytes. Similarly, respiratory rates were inhibited at lower lead concentrations in cerebral cortical slices from 8-day-old rat pups compared to those from adults. We conclude that primary cultured brain cells are appropriate in vitro systems for studying the in vivo cellular responses to lead. As in vivo, neurons are more sensitive than astrocytes to lead toxicity. In both cells, inhibition of aerobic energy metabolism appears to be closely associated with cell damage. The capacity of the astrocyte to sequester lead in nonmitochondrial intracellular sites may be critical in resistance to lead toxicity in vitro and in the mature brain.

Animals↗

PubMed1987

Brain cellular and mitochondrial respiration in media of altered pH.

This study was designed to investigate the effects of altered pH on cellular aerobic energy metabolism in the immature and adult rat cerebral cortex. Cerebral cortical slice respiration was measured polarographically in acid and alkaline media. In separate experiments, the extracellular pH was changed by altering the HCO3- concentration or the intracellular pH and extracellular pH were changed by altering the CO2. Respiratory rates and oxidative phosphorylation in adult rat cerebral mitochondria also were measured in media with an altered pH. Increased intracellular pH inhibited respiratory rates in cortical slices from immature rats more than in tissue from adults. Decreasing the pH to 6.7 produced no changes in respiration in mature cortical slices and moderate inhibition of immature tissue respiration. In cerebral mitochondria, altered pH caused inhibition of State 3 respiration, respiratory control ratios, and ADP/O ratios. These changes were greater and occurred with smaller pH changes in the alkaline compared to the acid direction. From the results of these studies, we conclude that brain cellular respiration is not affected by moderate decreases in intracellular pH. With increased pH, there is inhibition of cellular and mitochondrial respiration, which may be the mechanism for the rise in lactic acid previously observed to result from hypocarbia in vivo.

Aging↗

PubMed1987

Generation of altered transcripts by retroviral insertion within the c-myb gene in two murine monocytic leukemias.

Two murine monocytic leukemia cell lines, WEHI-265 and WEHI-274, were found to carry a rearranged c-myb gene. The rearrangements are due to insertion of a deleted Moloney murine leukemia virus (Mo-MLV) provirus in the 5' region of the c-myb gene and thus are similar to rearrangements in the ABPL tumors (G. L. C. Shen-Ong, M. Potter, J. F. Mushinski, S. Lavu, and E. P. Reddy, Science 226:1077-1080, 1984). In each cell line, the retroviral insertion has induced high levels of two aberrant RNA species, which, as in the ABPL tumors (G. L. C. Shen-Ong, H. C. Morse, M. Potter, and J. F. Mushinski, Mol. Cell. Biol. 6:380-392, 1986), contain both viral (Mo-MLV) and cellular (myb) sequences. Both species lack the sequences encoding the amino terminus of the c-myb protein and thus could encode a protein which, like the v-myb gene products (and the predicted ABPL myb proteins), is truncated at the amino terminus. We have found that the larger (5.3 kilobase [kb]) and more abundant of the tumor-specific myb RNAs was predominantly nuclear, while the smaller species (3.9 kb) was cytoplasmic. Furthermore, our data imply that the 3.9-kb RNA was derived from the 5.3-kb RNA by an additional splice which utilized a cryptic splice acceptor site within the viral gag sequences. On the basis of subcellular distribution and predicted translational potential, we conclude that the 3.9-kb RNA is probably the mRNA which encodes a truncated myb protein. We also show that, due to different insertion points in W265 and W274, the W274 myb RNAs contained sequences from a c-myb exon upstream of the exons represented in the W265 (and ABPL) RNAs. The significance of our findings with regard to transformation by myb in these tumors is discussed.

Base Sequence↗

PubMed1986

Energy-dependent volume regulation in primary cultured cerebral astrocytes.

Cell volume regulation and energy metabolism were studied in primary cultured cerebral astrocytes during exposure to media of altered osmolarity. Cells suspended in medium containing 1/2 the normal concentration of NaCl (hypoosmotic) swell immediately to a volume 40-50% larger than cells suspended in isoosmotic medium. The cell volume in hypoosmotic medium then decreases over 30 min to a volume approximately 25% larger than cells in isoosmotic medium. In hyperosmotic medium (containing twice the normal concentration of NaCl), astrocytes shrink by 29%. Little volume change occurs following this initial shrinkage. Cells resuspended in isoosmotic medium after a 30 min incubation in hypoosmotic medium shrink immediately to a volume 10% less than the volume of cells incubated continuously in isoosmotic medium. Thus, the regulatory volume decrease (RVD) in hypoosmotic medium involves a net reduction of intracellular osmoles. The RVD is partially blocked by inhibitors of mitochondrial electron transport but is unaffected by an inhibitor of glycolysis or by an uncoupler of oxidative phosphorylation. Inhibition of RVD by these metabolic agents is correlated with decreased cellular ATP levels. Ouabain, added immediately after hypoosmotic induced swelling, completely inhibits RVD, but does not alter cell volume if added after RVD has taken place. Ouabain also inhibits cell respiration 27% more in hypoosmotic medium than in isoosmotic medium indicating that the (Na,K)-ATPase-coupled ion pump is more active in the hypoosmotic medium. These data suggest that the cell volume response of astrocytes in hypoosmotic medium involves the net movement of osmoles by a mechanism dependent on cellular energy and tightly coupled to the (Na,K)-ATPase ion pump. This process may be important in the energy-dependent osmoregulation in the brain, a critical role attributed to the astrocyte in vivo.

Adenosine Triphosphate↗

PubMed1986

Late-onset Krabbe disease initially diagnosed as cerebroside sulfatase activator deficiency.

Clinical and biochemical findings in a male subject with progressive encephalopathy and peripheral neuropathy are presented. Early development was normal. At age 3.5 years, he had seizures associated with fever. Subsequently, there was progressive neurologic deterioration. A CT brain scan at age 4 years, 2 months demonstrated multiple areas of variable density in the white matter. There was mild slowing of nerve conduction velocities and a sural nerve biopsy revealed segmental demyelinative neuropathy. Metachromatic leukodystrophy was suspected, but arylsulfatase A activity in leukocytes and fibroblasts was in the normal range. The cerebroside sulfate loading test on intact cultured fibroblasts showed attenuated hydrolysis leading to a tentative diagnosis of cerebroside sulfatase activator deficiency. However, the attenuated response of proband fibroblasts was not normalized by supplementation with activator in a reproducible manner, and urine showed hyperexcretion rather than deficiency of activator. Ultimately, an assay for galactosylceramide beta-galactosidase activity established a deficiency of this enzyme leading to the diagnosis of late-onset Krabbe disease.

Cerebroside-Sulfatase↗

PubMed1986

Compliance with anticonvulsant therapy by epileptic youth. Relationships to psychosocial aspects of adolescent development.

Independence in daily life, family harmony as perceived by youths and their parents, and self-esteem were investigated in relation to anticonvulsant medication compliance in 25 epileptics aged 9-17 years. Medication compliance was assessed by monthly home saliva sampling for phenobarbital concentrations. Psychosocial issues were assessed by standardized instruments. Each psychosocial issue was highly correlated with compliance. Partial correlation analysis reveals that these findings are not explained by the subject's demographic or clinical characteristics. Medication noncompliance appears to be associated with a restriction of independence in daily life, lack of harmony in family relations, and low self-esteem in teenage epileptics. Clinicians should observe for these conditions and initiate patient and family counseling in order to maximize medication compliance and seizure control.

Adolescent↗

PubMed1984

Respiration in primary cultured cerebellar granule neurons and cerebral cortical neurons.

Respiration was measured polarographically in primary cultures enriched with cerebellar granule neurons or cerebral cortical neurons. The basal respiratory rate, measured on the sixth day after culturing, was 12.00 natom equiv. O/mg protein/min for the cortical neurons and 12.70 natom equiv. O/mg protein/min for the granule neurons. Maximal stimulation by 2,4-dinitrophenol produced a 20-40% increase over the basal rate for both neuronal types. Oligomycin inhibited neuronal basal respiration by 45%. These respiratory rates in neurons from primary culture are markedly lower than those measured in astrocytes grown under similar conditions.

Animals↗

PubMed1984

Effects of anticonvulsants on hyperthermia-induced seizures in the rat pup.

We studied the effects of phenobarbital (PB), valproic acid (VPA), and phenytoin (PHT) on the electroencephalograms and behaviorally defined seizure threshold temperatures in rat pups exposed to ambient hyperthermia on the fifth day of life. Animals injected with 10, 20, or 40 micrograms PB/g body weight (GBW) or 80, 150, or 300 micrograms VPA/GBW daily from the second day of life showed seizure temperature thresholds that were about 1.0 degree C higher than those of controls. Pups injected with PHT had thresholds that were equal to or lower than those in controls despite blood levels greater than 20 micrograms/ml. Preictal rhythmic sharp wave activity appeared in VPA-injected animals at temperatures below the threshold temperature. All experimental animals showed electrographic epileptiform activity at the threshold temperatures. We conclude that this animal model shows similar anticonvulsant efficacies to those found in human febrile seizures. This model may be useful in determining the efficacy of potentially useful anticonvulsant drugs and their mechanisms of action.

Animals↗

PubMed1984

Maturation of resistance to lead encephalopathy: cellular and subcellular mechanisms.

The rat pup fed inorganic lead has been studied extensively as an animal model of human lead encephalopathy. As in man, the sensitivity of the brain to lead toxicity is age-dependent. Pups given daily lead feedings for one week beginning in the first week of life show pathologic changes (i.e., hemorrhage, edema, and neuronal necrosis) throughout the brain including the cerebral cortex and cerebellum. Pups begun on daily lead feedings for two weeks between 10-18 days of age show similar pathologic changes almost entirely confined to the cerebellum. Pups receiving very large quantities of lead for two weeks beginning at 20 or 24 days of age develop only minimal edema or no changes by light microscopy. We have proposed that the effects of lead on cellular aerobic energy metabolism are important in the pathogenesis of the encephalopathy in the developing brain. Early in the course of lead feedings begun at 14 days of age, isolated cerebellar mitochondria show a loss of respiratory control. During the second week of lead feedings, respiration with NAD-linked substrates is inhibited in cerebellar mitochondria, but not in cerebral mitochondria, from these animals. Cerebral mitochondrial respiration in pups fed lead from birth also is inhibited while both cerebral and cerebellar mitochondrial respiration in lead-fed adults is not affected. Isolated brain mitochondria exposed to lead in vitro show similar changes; an initial respiratory stimulation (probably reflecting an energy-coupled uptake of lead) and a secondary inhibition of dehydrogenases located in the mitochondrial matrix. Lead also may compete with calcium for brain mitochondrial carrier or binding sites. During maturation, the brain appears to become resistant to lead toxicity by sequestering lead away from the mitochondrial site of action. This hypothesis is based upon the observations that: 1. the in vitro effects of lead are the same in immature and mature cerebellar mitochondria; 2. the cerebral and cerebellar lead concentrations are the same in immature encephalopathic and mature encephalopathy-resistant lead-fed animals and; 3. cerebellar mitochondria from animals fed lead from 14 days of age contain much more lead than cerebral mitochondria from these animals and cerebellar mitochondria from lead-fed adults. This hypothesis is supported further by the results of recent electron microscopic and elemental microprobe studies of lead distribution in the brains of animals fed lead beginning at 14-18 days of age.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗

PubMed1983

Breast self-examination competency: an analysis of self-reported practice and associated characteristics.

Of 308 Baltimore, Maryland women surveyed by telephone, 76.3 per cent reported having performed breast self-examination (BSE) during the last year, with only 35 per cent reporting monthly BSE. Four BSE ability scores showed that most women had little knowledge of the proper BSE technique. Utilization factors, socioeconomic status, and knowledge/attitude about cancer were not related to BSE competency. Higher BSE competency scores were related to performing BSE at the recommended interval, having been taught the procedure by a health professional, and perceived confidence in BSE practice were also related to proper performance.

Adult↗

PubMed1983

The practice and efficacy of breast self-examination: a critical review.

Evaluation of the results of breast self-examination (BSE) is inconclusive. Studies which address the question of proper method of BSE find that most women do not know how to carry out the procedure correctly. Socio-demographic characteristics most consistently related to BSE practice are age and education. New research on BSE must not only take into account such correlates but also provide some verification of the procedure to determine the importance of BSE in the detection and control of breast cancer.

Adult↗

PubMed1982

Rat cerebral cortical slice respiration in media of various osmolarities.

Freshly separated immature (5-day-old) and mature (60-day-old) rat cerebral cortical tissue demonstrates a Na+-dependent respiratory component similar to that recently described in primary cultured astrocytes. This respiratory component, which is not coupled to oxidative phosphorylation, increases as the osmolarity is increased above 354 mOsm in media with NaCl as the osmotic agent. With decreasing osmolarity from 354 to 80 mOsm, this respiratory component decreases more in cortical tissue than in cultured astrocytes. We propose that the respiratory response of neurons to decreasing extracellular osmolarity may differ from that of astrocytes in situ.

Animals↗

PubMed1982

Respiration and cell volume of primary cultured cerebral astrocytes in media of various osmolarities.

Respiration and cell volume of cerebral astrocytes from primary culture were measured in media of various osmolarities. Respiration was measured in 3T3 fibroblasts under similar conditions. Uncoupled respiration and respiration independent of oxidative phosphorylation were obtained by adding dinitrophenol and oligomycin, respectively. In NaCl media, dinitrophenol-stimulated respiration was inhibited at low and high osmolarities. With increasing osmolarity from 363 to 1185 mOsm, oligomycin-insensitive respiration increased and became the predominant respiratory component. The same respiratory changes in response to altered osmolarity were observed in 3T3 fibroblasts. In astrocytes, the oligomycin-insensitive respiration also increased in hyperosmolar sodium acetate media but was unchanged with increasing osmolarity in choline chloride or sucrose media. The increase in oligomycin-insensitive respiration in hyperosmolar NaCl media was blocked by amiloride, an inhibitor of passive Na+ movement. In contrast to amiloride, ouabain, an inhibitor of Na+, K+-ATPase, inhibited a constant amount of respiration with increasing NaCl concentration. The relationship of astrocyte volume to osmolarity was the same in hyper-osmolar media containing NaCl or sucrose. Cell volumes were greater in hypo-osmolar NaCl than in sucrose media. Our results suggest the presence of a Na+-dependent respiratory component in primary cultured cerebral astrocytes in media of increased osmolarity. This respiratory component is not coupled to oxidative phosphorylation or a Na+-K+-ATPase. It may be important in the proposed physiologic role of the astrocyte in maintaining brain extracellular water content and electrolyte concentrations.

Animals↗

PubMed1982

In vitro cellular respiration at elevated temperatures in developing rat cerebral cortex.

Cellular respiration in vitro was studied in cerebral cortical tissue from rats 2-60 days of age. Respiration was measured polarographically over the temperature range 34-44 degrees C in tissue slices in a basal condition; maximally stimulated by an uncoupler of oxidative phosphorylation, dinitrophenol; and inhibited by a blocker of mitochondrial oxidative phosphorylation, oligomycin. Basal respiration at 34 degrees C increased about 80% between 7 and 30 days of age. Oligomycin-insensitive respiration did not change with age. Dinitrophenol-stimulated respiration was unchanged from 2 to 10 days and then increased over 100% between 10 and 15 days of age. The Q10 for dinitrophenol-stimulated respiration increased from a value of 1 in tissue from rats 2-10 days of age to about 2 in tissue from rats 15 days and older. Our results confirm the previously reported maturational increases in basal respiration and in respiratory capacity in rat cerebral cortical tissue. The maturational increase in maximal respiratory capacity occurs in a short age interval coincident with a marked increase in the Q10 for the hyperthermic temperature range. Both these properties may be important in the increasing resistance to hyperthermia-induced seizures and their functional sequelae in the rat pup.

Animals↗

PubMed1982

Development of resistance to lead encephalopathy during maturation in the rat pup.

The purpose of this study was to determine the maturational period during which the rat pup becomes resistant to the toxic effects of lead on the brain. Pups were fed lead, as lead acetate, by esophageal catheter for 14 days beginning at various ages between 14-24 days. The daily lead doses, which produced a hemorrhagic cerebellar encephalopathy in at least 50% of pups, were 400 micrograms Pb/g body weight for animals fed from 14 days of age, 800 micrograms/g for animals fed from 16 days, and 1600 micrograms/g for animals fed from 18 days. In contrast, pups fed even higher lead doses beginning at 20 days showed only a patchy cerebellar edema by light microscopy while pups fed from 24 days had normal cerebellums by light microscopy. The encephalopathic lead doses in the younger pups resulted in the same cerebellar lead concentrations (about 30 micrograms/g protein) as the higher lead doses fed pups beginning at 20 ot 24 days. When corrected for blood lead concentrations, the cerebellar lead concentrations were 20-25% higher in the encephalopathic compared to the older encephalopathy-resistant animals. This difference may be accounted for by cerebellar hemorrhages in the younger animals. Polarographic studies showed inhibition of respiration in cerebellar slices from animals fed lead from 14 days of age but not in animals fed from 20 or 24 days of age. Our results that, during the encephalopathy-sensitive age period, a critical cerebellar concentration of lead is associated with the encephalopathy. Resistance to lead encephalopathy in older animals, with similar cerebellar lead concentrations, may be related to a capacity to sequester lead in new cellular locations away from its site of action on aerobic energy metabolism.

Age Factors↗