Biomedical subjects

M A Barry

Publications and source records attributed to M A Barry.

At least 55 records · Page 3Linked to original sources

PubMed1993

Identification of deoxyribonuclease II as an endonuclease involved in apoptosis.

Cell death occurs by apoptosis during programmed deletion of cells and following exposure to cytotoxic agents. Central to the mechanism of apoptosis is internucleosomal DNA digestion by an endogenous endonuclease which is thought to mediate cell death. An axiom of apoptosis is that the endonuclease involved is a Ca2+/Mg(2+)-dependent endonuclease. During purification of endonucleases from Chinese hamster ovary cells, we found little Ca2+/Mg(2+)-dependent endonuclease activity, but large amounts of an endonuclease active below pH 7. This acidic endonuclease was activated in intact cells by reducing intracellular pH values below 7 with a proton ionophore. This activity generated internucleosomal digestion of DNA characteristic of apoptosis. Nuclear extracts contained a cation-independent endonuclease with identical pH-dependent activity. We have compared the acidic endonuclease to bovine deoxyribonuclease II (DNase II) and have found them nearly identical by all tests, including sensitivity to various inhibitors, purification by the same chromatographic steps, and recognition by antibody raised against the bovine enzyme. Addition of either the acidic endonuclease or bovine DNase II to isolated nuclei induced internucleosomal DNA digestion up through pH 6.5. These data demonstrate that DNase II can mediate internucleosomal DNA digestion characteristic of apoptosis following intracellular acidification. Furthermore, these data question the premise that the Ca2+/Mg(2+)-dependent endonuclease is the only endonuclease involved in apoptosis.

Acid Phosphatase↗

PubMed1993

Persistence and calcium-dependent ATPase staining of denervated fungiform taste buds in the hamster.

Some fungiform taste buds in the hamster have been previously shown to persist for indefinite periods when deprived of their gustatory, chorda tympani (CT), innervation or both their CT and their trigeminal, lingual nerve, innervation (CT-L). The properties and numbers of persisting fungiform taste buds were examined 1 or 3 weeks after permanent CT or combined CT-L nerve cuts. The purpose was to reveal the status of taste buds at a time (3 weeks) when regenerating nerve fibres would normally be expected to reinnervate the epithelium. Denervated taste buds retain many normal characteristics including the pattern of histochemical staining for ectocalcium-dependent ATPase (Ca-ATPase). Taste-bud cells (including basal cells) have an intensely Ca-ATPase stained core surrounded by lightly stained peripheral cells. The Ca-ATPase stain was used to help identify and to define the size of the taste-bud core in denervated taste buds. Following CT-L or CT denervation most taste buds persisted; however the size of the taste-bud core was dramatically reduced. Fungiform taste buds differed in size based on their location in one of three tongue regions. The percentage decrease in size after denervation was also region specific and about the same for CT-L or CT cuts, suggesting that trigeminal fibres have no trophic effect on taste buds. However, trigeminal denervation caused a reduction in the number of persisting taste buds relative to CT denervation alone, which may be due to damage because of the loss of somatosensation.

Animals↗

PubMed1993

Loss and recovery of sodium-salt taste following bilateral chorda tympani nerve crush.

The ability of the gustatory system to recover following peripheral nerve injury was investigated in adult hamsters. A conditioned taste aversion paradigm was utilized to test sodium salt-taste function after bilateral crush of the chorda tympani nerve and after nerve regeneration. Bilateral chorda tympani crush abolished expression of a previously learned conditioned taste aversion to 0.1 M NaCl. At 10 to 16 weeks following surgery, the hamsters were reconditioned three times to 0.1 M NaCl. The hamsters were able to relearn the conditioned taste aversion and by 16 weeks, the crush and sham groups showed equally strong and specific aversions to 0.1 M NaCl. A second surgery to cut the regenerated chorda tympani nerves resulted, again, in the loss of expression of the conditioned taste aversion. Thus, regenerated chorda tympani nerves are capable of carrying the information needed to form a conditioned taste aversion specific for sodium salts in the adult hamster.

Animals↗

PubMed1992

Endonuclease activation during apoptosis: the role of cytosolic Ca2+ and pH.

An axiom of apoptosis is that increases in cytosolic Ca2+ activate a Ca2+/Mg(2+)-dependent endonuclease. However, when HL-60 human promyelocytic leukemia cells were incubated with the Ca2+ ionophore ionomycin in varied extracellular Ca2+, DNA digestion was independent of extracellular Ca2+. Under these conditions, intracellular Ca2+ concentrations did not correlate with the observed DNA digestion. In contrast, intracellular acidification correlated well with DNA digestion. These data indicate that increased intracellular Ca2+ is not the primary signal for endonuclease activation in all forms of apoptosis, but that intracellular acidification may be involved. The observed intracellular acidification is consistent with the involvement of deoxyribonuclease II in apoptosis.

Calcium↗

PubMed1992

Response of the gustatory system to peripheral nerve injury.

Peripheral taste nerve damage occurs as a result of disease and surgery. The response depends on the taste field affected and the species. Nerve regeneration is robust after the nerve is crushed or after it is cut if the severed ends are anastomosed. Taste buds, which appear after nerve regeneration, may be derived from dormant stem cells outside of taste buds or from remnants of taste buds that persist following denervation. Sprouting by intact taste nerves into denervated fields apparently does not occur. Regenerated primary afferents have taste response specificity, but it is unknown if neural response types are retained peripherally or centrally. Recent behavioral studies show specific deficits following loss of restricted taste fields in rodents, but little is known about recovery after nerve regeneration. Specific deficits have not been demonstrated in humans, although taste sensitivity has been correlated with numbers of taste buds. Enigmas such as these may be solved once the response of the central nervous system to gustatory nerve injury is defined.

Animals↗

PubMed1992

Ecto-calcium-dependent ATPase activity of mammalian taste bud cells.

Histochemistry was utilized to characterize Ca-ATPases associated with lingual taste buds in the golden hamster. Taste buds showed elevated staining for magnesium- or calcium-dependent ATPase (Ca-ATPase) relative to the surrounding epithelium. At low calcium concentrations (0.1-0.5 mM), intracellular staining predominated. Most of the studies were conducted at calcium concentrations of > or = 10 mM, in which most of the staining was localized to the external face of plasma membranes of taste bud cells (including receptor and basal cells) located in the core of fungiform taste buds, or the entire vallate or foliate taste buds. The peripheral fungiform taste bud cells stained much less intensely, but the peripheral cells adjacent to the core showed intermediate levels. GTP and ITP were just as effective substrates as ATP. Millimolar concentrations of magnesium were as effective as calcium. Inhibitors of intracellular ATPases, including quercetin, sodium azide, and 2,4-dinitrophenol, had no effect on the staining. Therefore, the Ca-ATPase staining of plasma membranes at mM concentrations of calcium is thought to correspond to one or more ecto-Ca-ATPase activities with unknown functions. Roles related to increased energy requirements or to the possible function of ATP as a neurotransmitter or -modulator are proposed.

2,4-Dinitrophenol↗

PubMed1992

The origins of DNA breaks: a consequence of DNA damage, DNA repair, or apoptosis?

DNA breaks can arise from many sources after incubation of cells with toxic agents. Very few agents break DNA directly, rather most breaks occur as a result of metabolic participation by the cell, such as during attempts to repair the damage. It is now realized that many DNA breaks arise as a consequence of steps in the pathway of cell death. Upon reanalyzing the methodology commonly used to detect DNA breaks, it is evident that many studies would not have observed DNA breaks associated with cell death. Frequently experimental conditions have been used that are extremely toxic to cells with the justification that the cells were still viable as measured by their ability to exclude dyes such as trypan blue. However, the DNA digestion associated with cell death by apoptosis occurs prior to changes in membrane integrity. Because the possibility of endogenous endonuclease activity was not realized, many studies may have inaccurately assumed that DNA breaks arose during, for example, inhibition of DNA repair or as intermediates in recombination. In light of the new understanding of apoptosis and the formation of DNA breaks as an early event in cell death, it is important to both reevaluate past conclusions and to ensure that future studies fully consider the breaks derived from the cytotoxicity of every agent under investigation.

Animals↗

PubMed1990

Activation of programmed cell death (apoptosis) by cisplatin, other anticancer drugs, toxins and hyperthermia.

Cell death induced by cisplatin was studied in Chinese hamster ovary cell lines, one proficient and the other deficient (100-fold sensitive) in DNA excision repair. Previous experiments demonstrated that cells progressed to and arrested in the G2 phase of the cell cycle before dying. DNA double-strand breaks were detected following G2 arrest and prior to loss of membrane integrity. These DNA breaks have been studied in more detail. DNA fragments were observed consisting of multimers of approximately 180 base pairs. These fragments are consistent with internucleosomal cleavage of chromatin by an endonuclease. At LC90 concentrations, DNA digestion began 48 hr cisplatin treatment followed by loss of membrane integrity and cell shrinkage 24 hr later. High concentrations of cisplatin (170 logs of kill) induced DNA digestion 12 hr after drug treatment but loss of membrane integrity occurred 12 hr later. Both cell death and DNA fragmentation were inhibited by cycloheximide, suggesting the requirement for new protein synthesis. Cells incubated with many other agents demonstrated the same characteristic pattern of DNA degradation. At 90% lethal conditions, DNA digestion was induced within 30 min by hyperthermia, 18 hr by methotrexate, and 48-72 hr by all other agents tested. DNA digestion always preceded loss of membrane integrity and cell shrinkage. These observations are consistent with cell death occurring by the process of apoptosis, or prorammed cell death, and demonstrate the importance of DNA digestion as an early and presumably essential step in cell death. The results suggest that, irrespective of the primary site of action of a drug, cell death by most pharmacologic agents is mediated by activation of the signal transduction pathway for apoptosis. The results also suggest two signal pathways for apoptosis, one directly associated with drug action and a second that requires cell cycle-related events.

Animals↗

PubMed1990

Analysis of events associated with cell cycle arrest at G2 phase and cell death induced by cisplatin.

DNA is the accepted target for cisplatin, but recent evidence has shed doubt on DNA synthesis as the critical process. L1210/0 cells incubated for 2 hours with cisplatin progress to the G2 phase of the cell cycle and are arrested there for several days. They then either progress in the cell cycle or die. In cells that eventually die, total transcription, polyadenylated [poly(A)+] RNA synthesis, and protein synthesis were markedly inhibited only after 48 hours. Nicotinamide adenine dinucleotide (NAD) and adenosine triphosphate (ATP) levels decreased after 3 days. Cell membrane integrity was lost after 4 days. These results demonstrate that cells can be lethally damaged, yet continue to undergo apparently normal metabolic activities for several days. In a previous study, DNA double-strand breaks were detected after 1 day. We now show that by 2 days, breaks are visible as fragmentation in the nucleosome spacer regions of chromatin. This type of damage is consistent with cell death occurring by the process of apoptosis. Cell shrinkage and morphology were also consistent with this type of cell death. The slow cell death reported here appears to occur at the G2/M transition and may involve events that normally occur at this stage of the cell cycle. These results demonstrate the importance of DNA degradation as an early and possibly essential step in cell death.

Adenosine Triphosphate↗

PubMed1990

Projections of giant fibers, a class of reticular interneurons, in the brain of the silver hatchetfish.

Giant fibers are large reticular interneurons that mediate excitatory input from the Mauthner cells to pectoral-fin motoneurons. The present study revealed extensive giant-fiber projections to central targets other than the pectoral-fin motoneurons. Physiologically identified giant fibers were filled intracellularly with Lucifer Yellow. The presence of numerous dendrites suggests that there may be significant integration of non-Mauthner inputs in the giant-fiber cell body. The axon decussates and then bifurcates to form a descending process, that innervates pectoral-fin motoneurons, and an ascending process with collaterals that terminate in the rostral trigeminal, rostral facial and, in some cases, oculomotor and trochlear motor nuclei. The projections are consistent with a role for the giant fibers as mediators of all the cranial components of the Mauthner-initiated startle response. There are also extensive projections to cells near the Mauthner cell and to the medial reticular formation. The latter projections may participate in longer-latency components of the Mauthner-initiated startle response, or they may constitute part of a general arousal pathway. The morphology of giant fibers suggests that they are homologous to cranial relay neurons in the goldfish and T reticular interneurons in zebrafish larvae. Non-Mauthner inputs to giant fibers may participate in non-Mauthner startle responses and contribute to the variability of Mauthner-mediated startle responses.

Animals↗

PubMed1990

Tuberculosis infection in urban adolescents: results of a school-based testing program.

In 1986-87 a pilot tuberculosis (TB) skin testing program was introduced for seventh and tenth grade students in the Boston (Massachusetts) public schools. The 8.9 percent tuberculin positivity rate in tenth grade students was significantly higher than the 5.1 percent rate found in seventh graders. A majority of those who were skin test positive were born outside the United States. These results suggest that tuberculin testing in an urban school setting may identify a significant number of candidates for TB preventive therapy, particularly among tenth grade students and those who are foreign-born.

Adolescent↗

PubMed1990

Prevalence of markers for hepatitis B and hepatitis D in a municipal house of correction.

Following an outbreak of hepatitis B (HBV) in a municipal house of correction, HBV markers were detected in 173/406 (43 percent) inmates and 10/129 (8 percent) staff. Of the 173 HBV-infected inmates, 14 (8 percent) had hepatitis D (HDV) markers compared to 0/10 staff members. Intravenous drugs use (IVDU) was most strongly associated with HBV marker presence. Increasing duration of imprisonment, history of hepatitis B and especially IVDU were associated with the prevalence of HDV markers.

Adult↗

PubMed1989

Increased suppressor T cells in probable transmitters of human immunodeficiency virus infection.

To evaluate behavioral and immunologic factors related to transmission of human immunodeficiency virus (HIV) by homosexual intercourse, we studied a population of 329 homosexual/bisexual men (155 partner-pairs) seen in a community health center and medical outpatient clinic. Logistic regression analysis showed that behavioral risk factors for infection in the 130 HIV-infected men included: receptive anal intercourse (OR 4.6, 95% CI-1.8, 12.1); receptive fisting (OR 2.5, CI-1.1, 7.0); nitrite use (OR 2.3, CI-1.2, 4.6); history of gonorrhea or syphilis (OR 2.3, CI-1.4, 3.9); and history of sexual contact with men from areas with many AIDS cases (OR 1.9, CI-1.0, 3.5). Comparing seven men who were probable transmitters of HIV and 11 men who had not transmitted HIV to their uninfected partners despite unprotected insertive anal intercourse, we found no differences in HIV isolation from peripheral blood mononuclear cells, circulating HIV antigen detection, or presence of neutralizing antibody to HIV. Helper T-cell numbers were not significantly different between the two groups, but transmitters had more suppressor T-cells than did nontransmitters.

AIDS-Related Complex↗

PubMed1988

The elasmobranch spiracular organ. I. Morphological studies.

The spiracular organ is a lateral line derived receptor associated with the first gill cleft (spiracle). Its functional morphology was studied in the little skate, Raja erinacea, and a shark, the smooth dogfish, Mustelus canis, with light and electron microscopy. The spiracular organ is a tube (skate) or pouch (shark) with a single pore opening into the spiracle. The lumen is lined with patches of sensory hair cells, and filled with a gelatinous cupula. In the little skate, hair cells form synapses with afferents but apparently not with efferent fibers. In both species, the spiracular organs are deformed by flexion of the hyomandibular cartilage at its articulation with the cranium. The hyomandibula is a suspensory element of the jaws; hyomandibular flexion results in jaw protrusion. The little skate spiracular organ is anchored at one end to the cranium and at the other to the hyomandibula so that it is stretched or relaxed during hyomandibular extension and flexion, respectively. In Mustelus, the effects of hyomandibular flexion on the spiracular organ are mediated indirectly by the superior post-spiracular ligament which inserts on the distal end of the hyomandibula. Deformation of the dogfish shark cupula during hyomandibular movement was observed. In the little skate, as revealed by transmission electron microscopy, there is a measurable deflection of the hair cell ciliary bundles from spiracular organs fixed with the hyomandibula in the flexed relative to the extended positions. In both species, hyomandibula flexion should result in hair cell depolarization, and sensory afferent excitation, based on the direction of the observed (skate) or expected (shark) deflection of hair cell cilia.

Animals↗

PubMed1988

The elasmobranch spiracular organ. II. Physiological studies.

The spiracular sense organs of the little skate, Raja erinacea, and the smooth dogfish, Mustelus canis, respond to movements of the hyomandibula-cranial joint. Afferent activity was recorded from the spiracular organ nerve in isolated preparations consisting of at least part of the cranium, the hyomandibula, and the spiracular organ and nerve. Afferents are excited by hyomandibular flexion at its joint with the cranium. Single unit recordings in the little skate revealed a single class of units that were slowly adapting, and had a regular firing pattern. Single unit firing rate increased up to about 70 spikes/s during hyomandibular flexion from a spontaneous rate at rest of 15-20 spikes/s, and could often be silenced by hyomandibular extension. The direction of excitation is consistent with the orientation of the hair cell ciliary bundles observed in morphological studies (Barry et al. 1988). Local deformations of the cupula are sufficient to excite or inhibit primary afferent firing, and volume changes in the spiracular organ as a whole are not necessary. The spiracular organs are relatively insensitive to electrical stimuli, vibration, or water movement. In conclusion, the spiracular organ functions as a sensitive joint receptor.

Animals↗

PubMed1988

Patterns of blood donations among individuals at risk for AIDS, 1984.

Of 978 respondents to an anonymous questionnaire targeted to reach homosexuals in Boston during October 1984, 88 (9 per cent) reported recent blood donation. When compared to non-recent donors, high-risk respondents who were recent blood donors were younger, less open about their sexual preference, and more likely to obtain their information about AIDS (acquired immunodeficiency syndrome) from television and newspapers. These results suggest that particular subgroups of the population at risk for AIDS would benefit from expanded educational programs.

Acquired Immunodeficiency Syndrome↗

PubMed1988

Medical costs of ambulatory patients with AIDS-related complex (ARC) and/or generalized lymphadenopathy syndrome (GLS) related to HIV infection, 1984-85.

A cost-of-illness study July 1, 1984-June 30, 1985 evaluating 28 patients with AIDS-Related Complex (ARC) and/or Generalized Lymphadenopathy Syndrome (GLS) found the average cost to be $489 per patient per year. None of the ARC or GLS patients in our study was hospitalized during the one year period, and none progressed to AIDS. No AIDS-specific treatment such as AZT was available at the time this study was completed.

AIDS-Related Complex↗

PubMed1988

Nosocomial infection and fatality in medical and surgical intensive care unit patients.

We prospectively studied 526 patients admitted to the medical intensive care unit (MICU) and 799 patients admitted to the surgical intensive care unit (SICU) at a municipal hospital over a 20-month period. Rates of nosocomial infection were higher in the SICU patients (31% vs 24%). The SICU patients had more urinary tract infections, bacteremias, and wound infections, and the MICU patients were older, had higher acute physiology scores on admission and were more often admitted with shock or coma. The SICU patients were more likely to have received prior antibiotic therapy and had significantly higher numbers of endotracheal tubes, arterial lines, central venous lines, and indwelling bladder catheters. Of the 23 variables univariately associated with nosocomial infection, only five remained significant after entry into step-wise regression models. The MICU patients had a higher fatality rate in the MICU than did the SICU patients (18% vs 10%), but the relative risk of a death following nosocomial infection was 3.5 for both groups. Thirty variables were significantly associated with hospital fatality; nine remained significant after analysis by stepwise logistic regression.

Aged↗