Showing papers by "University of Maryland, Baltimore published in 1977"

Evaluation of a UDP-Glucose-4-Epimeraseless Mutant of Salmonella typhi as a Live Oral Vaccine

Abstract: A mutant (Ty21a) of Salmonella typhi, which lacks the enzyme uridine 5'-diphosphate-glucose-4-epimerase, was evaluated in volunteers for use as a live attenuated oral typhoid vaccine. Five to eight doses of vaccine (containing 3-10(10) viable organisms per dose) were given to 155 men without significant side effects. The rate of excretion of the vaccine strain in stools was low, and the majority of isolations occurred on day 1 after vaccination. Revertants able to fement galactose were not found in any of 958 stool isolates tested. The mutant, strain Ty21a, grown in brain-heart infusion broth (BHIB) with 0.1% galactose, produces more O side chain than the same vaccine strain cultivated without galactose. Volunteers vaccinated with strain Ty21a grown in galactose and then challenged with 10(5) virulen S. typhi were significantly protected from disease and also had decreased stool carriage of S. typhi as compared with controls. Strain Ty21a grown without galactose did not provide vaccinees significant protection nor decrease fecal excretion of S. typhi as compared with controls. Strain Ty21a, when grown in BHIB with 0.1% galactose, results in a safe, stable and protective oral vaccine that warrants further study in field trials.

Gating of neuronal transmission in the hippocampus: efficacy of transmission varies with behavioral state

Abstract: Electrical stimuli were applied to the angular bundle of the freely moving rat, and the neuronal responses were recorded ipsilaterally in the dentate gyrus and the CA1 field of the hippocampus. The number of neurons responding monosynaptically in the dentate gyrus was relatively small when the animal was alert and not moving but was much greater both during slow-wave sleep and during rapid eye movement sleep. In Ca1, however, the trisynaptic population response was considerably smaller during rapid eye movement sleep and when the animal was alert than during slow-wave sleep. These findings are interpreted in terms of a set of behaviorally dependent "neural gates". Measurement of the synaptic current at the dentate gyrus induced monosynaptically by stimulation of the angular bundle further suggests that the mechanism by which gating occurs at this level is either a tonic inhibitory synaptic influence exerted upon the granule cells during the alert state, a tonic excitatory influence during slow-wave sleep, or both.

Cellular events during partial cerebral ischemia. I. Electron microscopy of feline cerebral cortex after middle-cerebral-artery occlusion.

Abstract: The feline right cerebral hemisphere was subjected to regional (incomplete) ischemia after clipping the middle cerebral artery for 5, 10, 15, 30 or 60 min, respectively. After each ischemic episode, a 10-min recirculation period was allowed, following which the brain was fixed and processed for electron microscopy. The earliest alterations, detected in the cerebral cortex after 15 min, increased in severity with longer ischemic episodes and were distributed multifocally. There was: (a) marked neuronal mitochondrial matrical swelling and progressive condensation of cytoplasm and nucleoplasm; (b) cytoplasmic swelling of astrocytes with preservation of glial mitochondrial volume; (c) capillaries, oligodendrocytes, myelin sheaths and axis cylinders did not change significantly, even after the longest interval studied: 60 min. This type of tissue reaction appears to be common for those forms of cerebral ischemia, in which circulation is either sustained partially (via collateral arteries) or restored after a period of absolute ischemia. Under these conditions, as yet undefined permeability changes in cell membranes lead to pronounced volumetric alterations of cellular compartments. Although no softening is detectable by digital examination, we suggest that such a set of structural abnormalities constitutes encephalomalacia, or the earliest stage of a lesion which is designated infarction, once it reaches irreversibility.

Mechanism of action of luteinizing hormone and follicle-stimulating hormone on the ovary in vitro.

Abstract: The mechanism of action of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) upon various cell types of the mammalian ovary is reviewed. Emphasis is placed upon in vitro studies using organ and cell culture as well as short-term incubations. FSH and LH actions upon the following ovarian functions are discussed: steroidogenesis and metabolism of the ovary as a whole and of the isolated follicle and its component cell types, the granulosa and thecal cells, as well as folliculogenesis and follicular growth, oocyte maturation, follicular rupture, and corpus luteum maintenance and steroidogenesis. The roles of gonadotropin receptors, AMP, prostaglandins, protein kinase, and protein synthesis in these LH and FSH actions are discussed. Intra-ovarian regulation of LH and FSH action is reviewed, including a discussion of the possible roles of follicular fluid inhibitors upon oocyte maturation and granulosa cell luteinization.

Spinal cord injury. The role of vascular damage in the pathogenesis of central hemorrhagic necrosis.

Abstract: • We postulated that damage to the endothelial lining of the spinal cord vasculature is a major factor in the pathogenesis of the characteristic lesion of the spinal cord (progressive, central, hemorrhage necrosis) that occurs after acute trauma. Endothelial damage may occur as a result of primary injury to the vessels or after arterial spasm. This damage results in deposition of platelets and formation of thrombi on the exposed subendothelial tissues and embolization of such thrombi to smaller vessels of the spinal cord parenchyma.

Ultrastructure of pericytes in mouse heart.

Abstract: The pericytes of mouse myocardium are extensively branched cells that form an incomplete layer around the endothelium of capillaries and postcapillary venules. The membranes of pericytes and endothelial cells are connected by specialized junctions. Microtubules, intermediate (10-nm) filaments and microfilaments are oriented within circumferentially-arranged cytoplasmic processes of pericytes so as partially to encircle the endothelial cylinder. The intracellular organization of these myocardial pericytes suggests that they are smooth muscle-like cells which may be capable of influencing microvascular dynamics in the heart.

Fructose-1,6-bisphosphate, a regulator of metabolism

Abstract: Fructose-1, 6-bisphosphate affects the rate of a large variety of enzyme reactions. In some instances its role as a physiologic effector is well documented. In many cases the effects of fructose bishosphate on particular enzymes have been demonstrated in vitro but the link to physiologic conditions has not yet been established. It is the purpose of this paper to summarize the scattered findings in fructose bisphosphate as an effector of enzyme reactions and to draw some conclusions about the role of the compound in metabolic regulation.

Mechanism for histamine H2-receptor induced cell-cycle changes in the bone marrow stem cell.

Abstract: The treatment in vitro of mouse bone marrow cells with 4-methylhistamine triggered the hematopoietic stem cell (CFU-S) from the G0 state into the S-phase of the cell cycle. In contrast, 2-methylhistamine had no such effect. Metiamide antagonized the effects of low concentrations of 4-methylhistamine. Antagonism by metiamide was reversed by high concentrations of 4-methylhistamine. Imidazole, and activator of phosphodiesterase, also suppressed the cell-cycle effects of 4-methylhistamine. The latter findings suggests that cyclic nucleotides may mediate in the stem cell response to 4-methylhistamine. Blocking the metabolism of endogenous histamine with a combination of aminoguanidine and chloroquine also initiated DNA synthesis in the bone marrow stem cell. Metiamide antagonized the effects of the aminoguanidine/chloroquine combination. These experiments associate a histamine H2-receptor with the hematopoietic stem cell. They also suggest that, if available, endogenous histamine can initiate cell-cycle changes in the pluripotent bone marrow stem cell.

Synaptic responses mediated by identified histamine-containing neurones

Abstract: EFFORTS to prove that histamine has a role in synaptic neurotransmission have been less successful than for other biogenic amines. For example, there has been no convincing physiological or pharmacological evidence to support the transmitter candidacy of this imidazole at any known synapse. In the central nervous system (CNS) of the marine mollusc Aplysia californica chemical measurements of single isolated neurones have revealed large concentrations of histamine within two identified neurones1. The histamine-containing neurones (HN) uniquely possess a specific histidine decarboxylating enzyme and they can synthesise and store labelled histamine2. These biochemical observations prompted the suggestion2 that the two identified nerve cells utilise histamine as a neurotransmitter. The physiological studies reported here show that each HN monosynaptically elicits multicomponent excitatory and inhibitory postsynaptic potentials (p.s.ps) in different follower neurones, the somal membranes of which show appropriate potential changes to iontophoretic application of histamine. This suggests that histamine is a neurotransmitter released from the nerve terminals of the HN.

The ultrastructure of "brain death". II. Electron microscopy of feline cortex after complete ischemia

Abstract: Permanent, complete global cerebral ischemia was induced in cats by filling the cardiovascular system with a plasma substitute (37° C). At variable intervals and up to 120 min thereafter, these feline brains were perfused with aldehydes and processed for electron microscopy. The resulting cellular alterations were homogeneous and uniform throughout the entire brain; they included early chromatin clumping, gradually increasing electron lucency of the cell sap, distention of endoplasmic reticulum and Golgi cisternae, transient mitochondrial condensation followed by swelling and appearance of flocculent densities, and dispersion of ribosomal rosettes. The marked contrast between the structural alterations in permanent, complete ischemia and incomplete cerebral ischemia, suggest differences in their pathogenesis. A basic determinant factor of the structural changes appears to be the volume of flow (serum, plasma, other) which is available at the time of the injury. This analysis of global cerebral ischemia provides some insight on the nature of cellular changes occurring shortly after somatic death.

Event related potentials and time estimation.

Abstract: Event related potentials (ERPs) recorded from the scalp of man were studied during a time estimation task. The principal ERP correlate of mental activity associated with time estimation appeared to be a CNV wave followed by a late positive shift. Latency of CNV termination was correlated with temporal judgments. There was some evidence that the onset of CNV termination occurred prior to the estimated time of occurrence of cortical motor command signals associated with production of the temporal judgments.

The Treatment of Perceptual Disturbances in Schizophrenia with Naloxone Hydrochloride

Abstract: The authors treated 12 schizophrenic patients who had overt hallucinatory symptoms with intravenously administered naloxone hydrochloride, a narcotic antagonist purported to have antihallucinatory properties. They found no evidence of the effectiveness of naloxone in preventing hallucinations over that of placebo when administered in a randomized, double-blind fashion.

Patterns of relapse in stages I, II and IIIA Hodgkin's disease: influence of initial therapy and implications for the future.

Abstract: An analysis was undertaken of the patterns of relapse observed among 111 patients with Stages I–IIIA Hodgkin's disease All had undergone staging laparotomy and then received either extended field irradiation alone (60%) or limited field irradiation followed by MOPP (nitrogen mustard, vincristine, procarbazine and prednisone) chemotherapy A total of 26 relapses occurred; relapse rates after irradiation alone were 34% but only 7% following irradiation plus adjuvant chemotherapy The duration of both remission and survival was significantly longer for the patients receiving irradiation plus chemotherapy than for those treated with irradiation alone ( p =

A modifier of (Na+ + k+) atpase in commercial ATP.

Abstract: WHEN most (Na+ + K+)ATPase preparations are allowed to hydrolyse ATP in the presence of different concentrations of Na+ and K+ ions, but with the sum [Na+] plus [K+] held constant, the behaviour observed is similar to that shown in the dotted curve of Fig. 1. K+ ions activate at low concentrations, and inhibit (by competing with Na+ ions at intracellular sites) at high concentrations. There is a broad plateau in the middle of the curve. We reported1 recently that (Na+ + K+)ATPase from the outer medulla of pig kidney showed behaviour of a different kind, like that shown in the solid curve of Fig. 1. Here, K+ ions apparently inhibit even at relatively low concentrations, so that, as the activating effect of K+ ions approaches saturation, the inhibitory effect becomes predominant and causes a sharp fall to an intermediate level of activity. This effect was more pronounced at 20 or 30 °C than at 37 °C, and at pH 7.5 than at pH 6.5. We have now discovered that this peculiar behaviour depends on the use of Sigma ‘Sigma grade’ ATP, and is not seen with Boehringer ATP (see Fig. 1). We report here that many samples of ‘Sigma grade’ ATP contain something which reacts with (Na+ + K+)ATPase reversibly and with a high affinity, making the enzyme much more sensitive to inhibition by K+ ions. The changed response to K+ ions, and the sensitivity of this response to pH can account for the inhibition of kidney (Na+ + K+)ATPase by ‘Sigma grade’ ATP reported by Charney, Silva and Epstein2, and the altered pH optimum reported by Katz and Michell3.

Studies of cellular recovery from injury. III. Ultrastructural studies on the recovery of the pars recta of the proximal tubule (P3 segment) of the rat kidney from temporary ischemia.

Abstract: The pars convoluta of the proximal tubule of the rat kidney was studied by light and electron microscopy during the recovery phase from transient ischemia. The left kidney was made ischemic by clamping the aorta just above the left renal artery leaving the blood supply to the right kidney and the intestine intact. The pars convoluta (P1 and P2 segments) of the proximal tubule was examined both immediately after various periods of ischemia (15, 30, 60 and 120 min) and after the same ischemic periods followed by 3, 6, 12 and 24 h of blood reflow ( = recovery phase). It was found that ischemia for periods up to 60 min were compatible with cell survival whereas 120 min of ischemia gave rise to irreversible cellular changes. Before regaining a normal conformation during the recovery phase, cells made ischemie for 15 min were characterized by slightly decreased cell height, dispersed nuclear chromatin, mitochondria in orthodox conformation and increased numbers of digestive vacuoles and of lipid droplets (stage A2). Most cells made ischemie for 15 min appeared normal when examined after 24 h of reflow. Cells made ischemie for 30 min were also characterized by stage A2 changes after 3 h of reflow and remained in this stage during all recovery periods studied. Cells made ischemie for 60 min first passed into a stage designated A1 and then later during the recovery phase into stage A2. Stage A1 cells were characterized by decreased height, condensed mitochondria, apparently increased numbers and sizes of secondary lysosomes and slightly dilated rough surfaced endoplasmic reticulum; 120 min of ischemia followed by reflow was not compatible with cell survival. Cells made ischemie for 120 min showed the following alterations denoted as stages C and D: shrunken with pyknotic nuclei, swollen mitochondria with large flocculent densities, and filled with different sized vesicles in the apical portion (stage C). Stage D included cells which had undergone necrosis, i.e., plasma membranes and organelles were fragmented and occurred as debris in the tubule lumens.

Alterations in nicotinamide and adenine nucleotide systems during mixed-function oxidation of p-nitroanisole in perfused livers from normal and phenobarbital-treated rats.

Abstract: The contents of adenine nucleotides as well as steady-state concentrations of a number of glycolytic, pentose phosphate-pathway and tricarboxylic acid-cycle intermediates were measured in extracts of livers from normal and phenobarbital-treated rats that were perfused with p-nitroanisole. Metabolites were measured in livers that were freeze-clamped during periods of maximal rates of drug metabolism. Treatment of rats with phenobarbital increased rates of p-nitroanisole O-demethylation approx. fivefold. The concentrations of lactate, xylulose 5-phosphate and ribulose 5-phosphate were increased by phenobarbital treatment, whereas that of fructose 1,6-bisphosphate declined. Perfusion of livers with p-nitroanisole produced significant increases in 6-phosphogluconate and ribulose 5-phosphate in livers from phenobarbital-treated rats, but not in livers from control rats. Treatment of rats with phenobarbital caused [NADP(+)]/[NADPH] to change in the direction of more oxidation, as calculated from measured concentrations of 6-phosphogluconate and ribulose 5-phosphate; however, the [NADP(+)]/[NADPH] ratio calculated from ;malic' enzyme was not changed. Additions of p-nitroanisole produced a reduction of NADP(+) as calculated from 6-phosphogluconate dehydrogenase activity, but did not alter the [NADP(+)]/[NADPH] ratio calculated from substrates assumed to be in equilibrium with ;malic' enzyme. Activities of both glucose 6-phosphate dehydrogenase and ;malic' enzyme were increased by phenobarbital treatment. NAD(+) became more reduced as a result of phenobarbital treatment; however, perfusion of livers with p-nitroanisole did not cause a change in the oxidation-reduction state of this nucleotide. Concentrations of adenine nucleotides in livers were not altered significantly by treatment of rats with phenobarbital; however, a significant decline in the [ATP]/[ADP] ratio occurred during mixed-function oxidation of p-nitroanisole in livers from phenobarbital-treated rats, but not in livers from normal rats. Perfusion of livers with two other substrates for mixed-function oxidation, hexobarbital and aminopyrine, produced an increase in the [NADP(+)]/[NADPH] ratio calculated from ;malic' enzyme. In contrast with livers perfused with p-nitroanisole, there was no significant change in adenine nucleotides in livers exposed to hexobarbital or aminopyrine. Addition of 2,4-dinitrophenol (25mum) to the perfusate containing aminopyrine decreased the [ATP]/[ADP] ratio and tended to prevent the oxidation of NADPH observed with aminopyrine alone. Thus in the presence of an uncoupler of oxidative phosphorylation, NADPH generation may exceed its utilization via mixed-function oxidation.

The characterization of histidine decarboxylase and its distribution in nerves, ganglia and in single neuronal cell bodies from the cns of aplysia californica

Abstract: — Histamine (HA) is present in substantial quantities in all ganglia of Aplysia californica. Within the cerebral ganglia this amine is known to be concentrated in at least two identified neurons designated C-2 neurons. In this study a combination of chemical and enzymatic analyses was employed to provide evidence for the existence of a biochemical pathway for HA synthesis in ganglia and individual neurons of this marine mollusk. Examination of extracts of individual neurons dissected from ganglia organ-cultured in the presence of [3H]histidine showed that every neuron accumulated labelled histidine, but only the HA-containing C-2 neurons synthesized and stored labelled HA suggesting that the formation of HA in Aplysia could be catalyzed by the enzyme histidine decarboxylase (HDC). HDC activity was studied with a new microradiometric assay. Many of the properties of the molluscan HDC studied were found to correspond to the vertebrate enzyme. Enzyme activity was inhibited by α-hydrazino-histidine but unaffected by concentrations of α-methyldopa or by 5-(3,4-dihydroxycinnamoyl) salicylic acid which produced nearly complete inhibition of aromatic amino acid decarboxylase activity. HDC was measurable in nervous but not other Aplysia tissues assayed. All 5 major ganglia contained HDC activity which spanned a 15-fold range between the least and most active ganglia. Only 4 of the 13 nerve trunks assayed yielded measurable enzymic activity; these active nerves were associated with the cerebral ganglia which has the highest HDC activity of all measured ganglia. Of the numerous individual neurons assayed for HDC, only the C-2 cells showed measurable enzyme activity, about 25 pmol/cell/h or 70 μmol/g protein/h. Since the activity of HDC in the HA-containing neurons was at least three orders of magnitude larger than all other neurons assayed in the cerebral and other ganglia, these data appear to provide a direct metabolic basis for the selective presence of HA in these cells, and they indicate that the cellular presence of HDC provides a useful biochemical marker for the location of HA-rich neurons in Aplysia.

Studies with a New Generation of Oral Attenuated Shigella Vaccine: Escherichia coli Bearing Surface Antigens of Shigella flexneri

Abstract: In an attempt to develop a safe, proliferating, oral, attenuated vaccine against shigellosis, genes that control the synthesis of group- and type-specific somatic antigens of Shigella flexneri 2a were transferred via conjugation to a recipient strain of Escherichia coli. The resultant hybrid (E. coli expressing shigella surface antigens) vaccine strain, PGAI 42-1-15, believed to have a complete (smooth) lipopolysaccharide, was given to volunteers in two vaccination-challenge studies. The vaccine was well tolerated and gave evidence of intestinal proliferation. In trial no. 1, volunteers given two doses of vaccine one month apart were challenged after eight weeks with 10(4) virulent S. flexneri 2a. Attack rates were comparable in vaccinees (50%) and controls (40%). In trial no. 2, vaccinees were given three weekly doses of vaccine and were challenged four weeks later with a small inoculum (10(2)) of S. flexneri 2a. Again, attack rates among vaccinees (47%) and controls (39%) were similar. It is unclear why this theoretically ideal, live shigella vaccine failed to protect against S. flexneri 2a.