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Biomedical subjects

D J Miller

Publications and source records attributed to D J Miller.

At least 163 records · Page 9Linked to original sources
PubMed1991

Synergism of histidyl dipeptides as antioxidants.

Histidyl dipeptides such as carnosine (beta-alanyl-L-histidine) and homocarnosine (gamma-amino-butyryl-L-histidine) are reported at millimolar concentrations in several mammalian tissues (O'Dowd et al., 1988; House et al., 1989), but their precise physiological function, or functions, is uncertain. These compounds are known to be potent buffers at physiological pH (Davey, 1960). They are also able to restore functional capacity to fatigued muscle preparations, stimulate some glycolytic enzymes and maintain coupling between mitochondrial oxidation and phosphorylation (Severin, 1964). Histidyl dipeptides may also have antioxidant activity, though this finding is controversial. For example, Aruoma et al. have argued that these compounds, individually, are unable to scavenge superoxide (O2-.), hydrogen peroxide (H2O2) or hypochlorous acid (HOCl) at rates which could offer antioxidant protection in vivo. Since there is a range of these histidyl dipeptides within mammalian tissue we have investigated possible synergism between them in respect of antioxidant activity. Our results show that combining histidine-containing compounds at near physiological concentrations results in synergistic antioxidant activity.

Anserine↗
PubMed1991

Simple phobia as a symptom of posttraumatic stress disorder in a former prisoner of war.

Behavioral, nonpsychoanalytic interventions for phobic conditions have shown to be quite effective in the reduction of symptomatology. This case documents that a combination of systematic desensitization, visual imagery, and in vivo exposure can reduce a phobic condition of 40 years duration. This intervention was shown to be effective even though the individual carried a concomitant diagnosis of posttraumatic stress disorder (PTSD).

Combat Disorders↗
PubMed1990

Nucleotide sequence of the histone H3-encoding gene from the scleractinian coral Acropora formosa (Cnidaria: Scleractinia).

The histone H3-encoding gene from the staghorn coral Acropora formosa has the 3'-hairpin structure which functions as termination/processing signal in nonpolyadenylated histone mRNAs. The predicted amino acid sequence is highly homologous with the major H3 histones of higher metazoans, and has least homology with the corresponding protist and fungal proteins. These data are inconsistent with the phylogenetic position which has been assigned to the Cnidaria by partial 18S rRNA sequence comparison.

Amino Acid Sequence↗
PubMed1990

Male accessory sex glands produce heparin-binding proteins that bind to cauda epididymal spermatozoa and are testosterone dependent.

Heparin binds to bovine sperm and stimulates capacitation in vitro. Seminal plasma alters the ability of epididymal sperm to bind heparin, and several heparin-binding proteins (HBPs) have been identified in bull seminal plasma. This study had three objectives: 1) to identify production sites of seminal plasma HBPs, 2) to determine which HBPs bound to cauda epididymal sperm, and 3) to determine whether presence of HBPs was testosterone dependent. Proteins from bull or rat seminal vesicles, prostates, and bulbourethral glands were separated by heparin affinity high-performance liquid chromatography. HBPs were found in all accessory glands of rats and bulls, but the major source of bovine seminal plasma HBPs appeared to be seminal vesicles. Between 25% and 50% of the protein from each gland bound to the heparin column, and NaCl concentrations required to elute proteins ranged from 0.15 to 1.4 M. One-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that major HBPs were relatively small, with molecular weights between 13 and 31 kDa, but some HBPs also exhibited higher molecular weights, between 40 and 100 kDa. Radioiodinated HBPs from each bovine gland were incubated with epididymal sperm. Labeled HBPs binding to sperm exhibited molecular weights of 14, 16, 24, and 30 kDa as determined by SDS-PAGE and autoradiography. The HBP content of the accessory sex glands decreased significantly in castrated rats and was restored to levels of sham-operated controls by testosterone replacement. Heparin-binding proteins may play a role in fertilization by attaching to sperm surfaces, enabling heparin-like glycosaminoglycans in the female reproductive tract to induce capacitation.

Animals↗
PubMed1990

Carbohydrates and fertilization in animals.

A frequently used mechanism for sperm-egg recognition in many species involves complementary protein-carbohydrate interaction. The usual paradigm includes complex glycoconjugates in reproductive tract fluids or on the eggs which are recognized by carbohydrate-binding proteins on the sperm surface. Various glycoconjugates are utilized in the steps of sperm capacitation, sperm binding to the egg extracellular matrix and vitelline membrane and induction of the acrosome reaction. Several types of complex glycoconjugates are involved in these processes, including proteoglycans, lactosaminoglycans, sulfated fucose-containing glycoconjugates, and glycoproteins. There appear to be some structural similarities between active glycoconjugates; they are large in molecular weight and complex, and they are often sulfated, fucosylated, and attached to a protein through serine or threonine residues. In some species, the protein core of the glycoconjugates also participates in the interaction by limiting the binding of carbohydrates to sperm only of the relevant species, likely by providing the proper steric arrangement for the interaction. In other cases the protein core seems to serve more as a crosslinker of the carbohydrate moieties. This review discusses the types of glycoconjugates implicated in fertilization and the complementary lectin-like proteins found on sperm.

Animals↗
PubMed1990

Analysis of carnosine, homocarnosine, and other histidyl derivatives in rat brain.

Isocratic reverse-phase analytical HPLC has been used to examine naturally occurring imidazoles of rat brain. Elution of brain extracts with a phosphate buffer mobile phase from columns packed with Hypersil ODS (5 microns) resulted in good separation of the well-documented brain imidazole-containing dipeptides carnosine and homocarnosine. Measured concentrations corresponded to published values. Several further peaks observed had properties consistent with those of N-acetyl derivatives of compounds related to carnosine and homocarnosine. N-Acetyl forms not commercially available were prepared and their identities verified by nuclear magnetic resonance spectroscopy. A number of these had chromatographic properties identical to those of compounds in brain extracts. Fractions corresponding to some of the peaks were examined using staining systems specific for certain chemical features and compared with results obtained for commercial or synthetic standards. The results of these tests supported the chromatographic data. Thus, chromatographic and microchemical evidence is presented for the existence of N-acetyl forms of histidine, 1-methylhistidine, carnosine, anserine, and homocarnosine in rat brain.

Acetylation↗
PubMed1990

The 'calcium sensitising' effects of ORG30029 in saponin- or Triton-skinned rat cardiac muscle.

1. The effects of a range of concentrations of ORG30029 (1 microM to 1 mM) were investigated on fully (Triton-treated) or selectively (saponin-treated) 'skinned' ventricle trabeculae from rat. The Ca-sensitivity was increased by 100 microM and amounted to a mean reduction in the Ca2+ necessary for half-maximal activation (1/Kapp) of 0.174 +/- 0.053 (mean +/- s.e.mean) pCa units. ORG30029 (50 microM) gave a smaller mean shift of 0.05 +/- 0.016 pCa units. A slight shallowing of the relationship between -log[Ca2+] (pCa) and steady-state tension was also generally found (mean Hill exponent reduction 0.37 +/- 0.28 at 100 microM). 2. The Ca-sensitizing action altered in a dose-dependent fashion. Judged by the ability to enhance force from an initial level of activation of 10-20% of maximum Ca-activated force (Cmax), the first significant effects occurred near 10 microM and continued to increase at 1 mM. 3. A small (3.7 +/- 1.1%) but consistent increase in Cmax was produced by ORG30029 at 100 microM. Much larger increases were produced by the drug at higher concentrations (up to 20-50% at 1 mM). 4. The consequence of these changes is that at levels of activation likely to occur in the heart, the absolute increase in force by 100 microM ORG30029 was considerable: it amounted to a 150-200% increase at a [Ca2+] producing 20% at Cmax. At this drug concentration virtually all the effect was due to Ca-sensitizing rather than increasing Cmax. 5. In the saponin-treated preparations, at concentrations up to 1 mM, ORG30029 did not release Ca from the sarcoplasmic reticulum, as indicated by the failure to evoke contracture under conditions where caffeine induced large responses. 6. At 100 microM, ORG30029 potentiated the transient, caffeine-induced contracture (saponin-treated preparation) to an extent consistent with the Ca-sensitizing effect seen under conditions of steady-state tension development.

Animals↗
PubMed1990

An examination of the sources of calcium for contractions mediated by postjunctional alpha 1- and alpha 2-adrenoceptors in several blood vessels isolated from the rabbit.

1. The roles of intracellular and extracellular-derived Ca2+ in alpha-adrenoceptor-mediated contractions to noradrenaline (NA) have been investigated in several isolated blood vessels from the rabbit by examining responses in the presence of a modified Krebs-Henseleit saline with 2.5 mM Ca2+ and a Ca2(+)-buffered saline with 0.1 microM free Ca2+. 2. NA was tested in preparations of the abdominal aorta, distal saphenous artery, renal vein, lateral saphenous vein, plantaris vein and ear vein exposed to a Ca2(+)-buffered saline with 0.1 microM [Ca2+]. A concentration of NA which was maximally effective in modified Krebs-Henseleit saline, produced an initial transient contraction (ITC) followed by a relaxation towards baseline. This is evidence that alpha-adrenoceptor-mediated responses in all these blood vessels depend upon calcium from both sources. 3. The ITC was particularly pronounced in the arteries and was associated more closely with the alpha 1-receptor subtype. In the abdominal aorta, distal saphenous artery and renal vein the ITC can almost exclusively be attributed to an alpha 1-adrenoceptor (prazosin-sensitive, rauwolscine-resistant). In the ear vein, and to a lesser extent the plantaris vein, the ITC was mediated in part by an alpha 2-adrenoceptor (prazosin-resistant, rauwolscine-sensitive). 4. alpha 2-Adrenoceptors in the lateral saphenous vein largely account for the response to NA in modified Krebs-Henseleit saline, but alpha 1-adrenoceptors mediate the ITC in Ca2(+)-buffered saline. After selective inactivation of alpha 1-adrenoceptors with a combination of phenoxybenzamine and rauwolscine, responses to NA in modified Krebs-Henseleit saline are slow in onset and there is no ITC in Ca2(+)-buffered saline. 5. The possible significance of the coupling of postjunctional alpha 2-adrenoceptors to dual sources of Ca2 + is discussed in relation to the interaction between alpha-adrenoceptor subtypes and the ease of demonstrating functional alpha 2-adrenoceptors in isolated blood vessels.

Animals↗
PubMed1990

The effects of taurine on Ca2+ uptake by the sarcoplasmic reticulum and Ca2+ sensitivity of chemically skinned rat heart.

1. Caffeine (10 mM) induced a transient contracture in saponin-treated cardiac trabeculae as a result of Ca2+ release from the sarcoplasmic reticulum (SR). Regular cycles of uptake and release were repeated to stabilize responses. The SR accumulated Ca2+ during the period prior to the addition of caffeine and this was reflected in the size of the caffeine contracture. Increasing the time for Ca2+ loading between successive caffeine exposures resulted in an increase in the amplitude of the contracture. Similarly, the size of the contracture was a function of the calcium ion concentration [( Ca2+]) in the preceding loading period. 2. Taurine (microM-40-mM), when included in both loading and caffeine solutions, markedly potentiated the caffeine-induced contracture. The effect occurs even if taurine was included only in the loading solutions. The potentiating effect was ascribed to a direct action of taurine on the SR, since taurine did not significantly change the [Ca2+] in the loading solutions. 3. The maximal effect of taurine was produced at approximately 5 mM; higher taurine concentrations caused a lesser potentiation of the caffeine contracture. If the solutions were balanced with respect to osmolarity the effect of taurine did not decline at high concentrations. 4. If the [Ca2+] in the loading solutions was increased to produce a caffeine-induced contracture that peaked close to maximal Ca2(+)-activated force, taurine caused a fall in the size of contracture and a more variable response. This result could be explained by an increase in the spontaneous release of Ca2+ from the SR in the presence of taurine. 5. In Triton-skinned trabeculae, taurine (1 mM-40 mM) increased the Ca2+ sensitivity of the contractile proteins in a dose-dependent manner but had little effect on maximum Ca2(+)-activated force. The increase in Ca2+ sensitivity was small: in a typical experiment 30 mM-taurine reduced the [Ca2+] necessary for half-maximal activation from 3.02 to 2.56 microM, with no significant change in the shape of the relationship.

Actin Cytoskeleton↗
PubMed1990

Continuous lidocaine infusion and focal feline cerebral ischemia.

We measured somatosensory evoked potentials, infarct size, and cerebral blood flow in 20 cats subjected to occlusion of the middle cerebral artery for 3 hours, followed by an equal period of reperfusion. The cats were randomized into a treatment group that received a continuous infusion of 2 mg/kg lidocaine hydrochloride or a control group that received an equivalent volume of normal saline. All 10 treated cats retained measurable evoked potentials throughout the experiment. In five control cats, evoked potentials disappeared completely at some point during the occlusion (difference between groups significant at p less than 0.001). Mean amplitude of the major cortical wave in the nine treated cats with cerebral infarcts was higher than that of the nine corresponding controls (p less than 0.05). Lidocaine reduced the mean +/- SEM size of the infarcts from 30.1 +/- 6.0% in the control group to 14.7 +/- 4.9% in the treated group (p less than 0.05). As blood flow was reduced in the infarct and peri-infarct zones in the control but not the treated cats, our results suggest that the beneficial effects of lidocaine may be due to preservation of blood flow in the ischemic zone.

Animals↗
PubMed1990

Habituation of phasic total respiratory resistance responses.

We examined the effects of repetitious stimulation on phasic respiratory resistance responses of 30 healthy adult males. Individuals were told either that they would inhale a substance which would cause bronchoconstriction or that they would inhale a substance which would cause no breathing changes. All subjects completed four inhalation trials. During each trial a lamp was turned on to indicate the presence of the inhalant; in reality, the subjects inhaled no substances. Respiratory resistance and functional residual capacity were measured just before and during the time the lamp was on. Regardless of the type of instruction, the response to the inhalation task was predominantly an increase in respiratory resistance. During Trials 1, 2, and 3, the number of subjects who increased respiratory resistance was greater than the number of subjects who decreased respiratory resistance. The number of subjects who increased respiratory resistance was not different from the number of subjects who decreased respiratory resistance during Trial 4. Changes in functional residual capacity did not affect changes in respiratory resistance; functional residual capacity changed neither within nor between trials. Given a progressive decrease in the number of subjects who increased their respiratory resistance on successive trials, the results were consistent with a response habituation model.

Adolescent↗
PubMed1990

Molecular and developmental biology of the Cnidaria--basic aspects and phylogenetic implications.

Cnidarians are generally considered to be the most primitive group of eumetazoans. They are therefore of considerable interest for comparative studies of metazoan development and evolution. The application of molecular techniques to cnidarians can provide important insights into developmental processes and phylogenetic relationships both within the phylum Cnidaria and among the eumetazoa. This paper reviews current knowledge of molecular and developmental biology of cinidarians with particular emphasis on tropical scleractinian corals and soft corals from the Great Barrier Reef region. Nucleotide sequencing of the histone gene cluster has unequivocally established that cnidarians are typical eumetazoans. Repeated sequence analysis has been applied to the staghorn corals, and implies a major divergence within this group, which corresponds with differences in sperm ultrastructure. Recent developmental studies of corals have indicated that some species have an unusual method of germ layer formation. Molecular events associated with this process, and with other important developmental stages, are currently under investigation. Other areas of current research interest, including targets for PCR-based investigations into cnidarian phylogeny, are highlighted.

Animals↗
PubMed1990

Fetal alcohol syndrome: review of the literature and case report.

Fetal Alcohol Syndrome (FAS) is now recognized as a reality for the unborn if the pregnant woman ingests alcohol during the gestation period. Significant oro-facial problems occur as well as mental and behavior problems. This article reviews the current thought on oro-facial and dental diagnosis and therapy.

Child, Preschool↗
PubMed1989

The contribution of mitochondrial calcium ion exchange to relaxation of tension in cardiac muscle.

The possible contribution of mitochondrial Ca2+ accumulation and release to contractile phenomena has been investigated. Two intracellular fractions of Ca2+ sequestration can be identified in cardiac myocytes, one ascribed to mitochondria. Two modes of Ca2+ transport exist within the mitochondrial fraction, one dependent upon mitochondrial respiration and the other upon extramitochondrial [Na+]. Experiments with trabeculae show that under appropriate conditions, the rate of relaxation and the amount of tension developed is dependent on these two modes of Ca2+ transport. A model is presented quantifying the contribution of the mitochondria to relaxation.

Animals↗
PubMed1989

Non-mitochondrial calcium ion regulation in rat ventricular myocytes.

Ca2+ exchange has been measured in a suspension of rat ventricular myocytes treated with digitonin or saponin to render the sarcolemma permeable to small molecules and ions. Two fractions of exchange were identified, one that was attributed to the mitochondrial component of the cell and the other to a non-mitochondrial fraction. Mitochondrial Ca2+ uptake was blocked by sodium azide and depended on respiratory substrates whereas non-mitochondrial uptake occurred independently of these molecules but was dependent on ATP and creatine phosphate. Non-mitochondrial Ca2+ uptake could be induced at a Ca2+ concentration below 1 microM and the initial rate increased with concentration up to 100 microM. Uptake could be reversed by sulmazole (a caffeine-like substance) and this reversal in turn inhibited by ryanodine. These properties suggest that the major locus for non-mitochondrial Ca2+ exchange is at the sarcoplasmic reticulum. Ca2+ exchange could be modulated by a number of agents, including carnosine, but was unaffected by others, including Na+, inositol trisphosphate and cyclic AMP. A kinetic model of the data is presented, which incorporates similar data of Ca2+ uptake into the mitochondrial fraction. The rates of Ca2+ exchange measured in these experiments suggest that these two components of the cell can reduce the sarcoplasmic Ca2+ concentration rapidly enough to account for the observed transient nature of the isometric twitch. Furthermore, it is suggested that both non-mitochondrial and mitochondrial fractions of the cell could significantly contribute to tension relaxation in rat cardiac muscle.

Animals↗
PubMed1989

Chemical N-desulfation of heparin negates its ability to capacitate bovine spermatozoa.

Heparin specifically and saturably binds to bovine spermatozoa and stimulates capacitation as assessed by the ability of spermatozoa to undergo a zona pellucida-induced acrosome reaction (AR) in vitro. However, the structural features of heparin important for capacitation are poorly understood. The purpose of this study was to determine the importance of the sulfate content of heparin for its potency to bind to bull spermatozoa and promote agglutination and capacitation. The pyridine salt of heparin was N-desulfated, which reduced its mean sulfate content from 19.7% to 11.6%. The N-desulfated heparin was then resulfated by incubation with trimethylamine sulfur trioxide for 6, 12, or 24 hr, raising sulfate to original concentrations. Heparin but not N-desulfated heparin competed with [3H]-heparin to bind to spermatozoa. Heparin at 11.6 micrograms/ml reduced [3H]-heparin binding by half when competing with a saturating concentration of the radiolabeled compound (12 micrograms/ml). N-desulfated heparin did not displace [3H]-heparin. Heparin, resulfated 6 hr or 12 hr, was equal to native heparin in binding potency. Heparin at 50, 100, or 250 micrograms/ml caused more than 40% of the cells to head-to-head agglutinate in aggregates of 8 or more. N-desulfated heparin did not cause agglutination. After spermatozoa were incubated with 0, 5, 10, 50, 100, or 250 micrograms/ml of heparin for 4 hr, 100 micrograms/ml of lysophosphatidylcholine (LPC)-induced AR within 20 min in 21.3, 37.7, 27.8, 45.3, 54.2, or 42.5% of the cells, respectively. Sperm exposed to the same concentrations of N-desulfated heparin exhibited AR of 17.7, 27.3, 24.3, 22.5, 27.7, or 33.8%, respectively, following exposure to LPC. Resulfated heparin did not agglutinate or capacitate spermatozoa. In conclusion, N-desulfation of heparin abolished heparin's ability to bind to, agglutinate, and capacitate bovine spermatozoa. Resulfation of N-desulfated heparin restored binding activity but not agglutination or capacitation activity.

Acrosome↗