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Biomedical subjects

F E Bloom

Publications and source records attributed to F E Bloom.

At least 127 records · Page 7Linked to original sources
PubMed1993

Distribution of parvalbumin immunoreactivity in the vertebrate retina.

Parvalbumin, a calcium-binding protein thought to buffer intracellular calcium, is expressed in selected neuronal and non-neuronal cell populations. We used a well-characterized antibody directed against parvalbumin to investigate the distribution of parvalbumin in the retina of twelve vertebrate species to evaluate patterns of cellular expression for recurrent functional features. Parvalbumin immunoreactivity was displayed by subpopulations of ganglion, amacrine, bipolar and horizontal cells in different species-specific combinations. In the pigeon retina, subpopulations of amacrine, ganglion and bipolar cells were immunoreactive for parvalbumin. Parvalbumin immunoreactive bipolar cells in this species were mostly confined to the temporal dorsal region of the retina. In the owl, no immunoreactive amacrine cells were found, but many bipolar cells displayed parvalbumin immunoreactivity. In the teleost retina, amacrine and ganglion cells were found to be immunoreactive for parvalbumin. A high degree of species-specific variation was encountered in the mammalian retina. The most consistent finding within this class was that subpopulations of parvalbumin-immunoreactive amacrine cells were consistently observed in every species. In the rabbit, horizontal and ganglion cells displaying parvalbumin immunoreactivity were also seen. In rodents (hamster, ground squirrel), parvalbumin immunoreactivity was displayed by subpopulations of amacrine cells and, in the squirrel, by some ganglion cells as well. In the cat and in the baboon retina, parvalbumin immunoreactivity was found in horizontal cells, ganglion cells and a subpopulation of amacrine cells. The distribution of parvalbumin immunoreactive neurons in the vertebrate retinae studied showed no systematic correlation with phylogenetic proximity. The expression of parvalbumin within the systems of retinal neurons may therefore reflect the functional needs of different visual behaviors.

Animals↗
PubMed1993

Chronic ethanol intake decreases vasopressin mRNA content in the rat hypothalamus: a PCR study.

Vasopressin mRNA content was studied by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in the hypothalami of rats chronically treated with ethanol (EtOH). Quantitative RT-PCR allows for the accurate measurement of peptide mRNA levels in discrete regions of the brain of individual animals. EtOH markedly reduced the level of vasopressin mRNA. Furthermore, salt loading was ineffective in inducing a significant increase in vasopressin mRNA level in EtOH-treated rats, unlike in controls. The present results suggest that EtOH not only decreases vasopressin mRNA content in the rat hypothalamus, but also impairs its capacity to respond to salt loading.

Alcoholism↗
PubMed1993

Oral alcohol self-administration stimulates dopamine release in the rat nucleus accumbens: genetic and motivational determinants.

Dopaminergic neurotransmission in the nucleus accumbens may be an important factor in ethanol reinforcement and genetically determined ethanol preference. This hypothesis was tested by measuring dopamine (DA) release by intracranial microdialysis during voluntary oral ethanol self-administration in alcohol-preferring (P) and genetically heterogeneous Wistar rats. The animals were trained to respond for ethanol (10% w/v) or water in a free-choice operant task. Extracellular DA levels in the nucleus accumbens were subsequently monitored during 30-min self-administration sessions and a 15-min "waiting period" before session onset. Ethanol self-administration in all animals was followed by a significant, dose-dependent rise in DA release with maximal effects at approximately 15 min after peak intake. Dose-effect functions revealed significantly steeper slopes for the DA-releasing effects of ethanol in P than in genetically heterogeneous Wistar rats. Over an identical range of ethanol doses and blood alcohol levels, increases in DA efflux ranged from 143% to 459% of basal levels in P rats but only from 142% to 212% in Wistar rats. To differentiate the pharmacological effects of ethanol from the effects of operant responding, additional groups of P and Wistar rats were tested during self-administration of saccharin (0.05% w/v). By contrast with ethanol, saccharin did not substantially elevate extracellular DA levels. A significant, transient increase in DA efflux was, however, observed in both strains of rats during the presession waiting period in the absence of ethanol or saccharin availability.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Noninvasive presurgical neuromagnetic mapping of somatosensory cortex.

Rapid presurgical neuromagnetic localization of the somatosensory cortex was performed successfully on five patients with a large-array biomagnetometer by a protocol called magnetic source imaging (MSI). Determination of the location of the central sulcus is important in assessing operative risk and determining the optimal operative approach to structural lesions in the vicinity of the motor strip. The use of magnetic resonance imaging anatomical methods and intraoperative visual identification can be imprecise, whereas invasive localization prolongs operative time, adds cost, and entails added risk. Until the recent development of large-array biomagnetometer systems, neuromagnetic localization of the central sulcus had been demonstrated in research but was so time consuming and laborious as to preclude routine clinical use. In this study, the validity of MSI localizations was confirmed intraoperatively by direct cortical recording of somatosensory evoked potentials and/or direct motor stimulation. Complete agreement was found between MSI and intraoperative mapping in locating the central sulcus. Objective confirmations considered together with the speed and reliability of the procedure and with the presurgical availability of the results suggests the potential utility of MSI for routine surgical planning.

Adult↗
PubMed1992

Expression of c-fos protein by immunohistochemically identified oxytocin neurons in the rat hypothalamus upon osmotic stimulation.

Double immunostaining for c-fos and oxytocin (OXY) was used to study the topography and time course of the metabolic activation of the hypothalamic oxytocinergic system upon osmotic stress in the male rat. Animals injected i.p. with hypertonic saline expressed c-fos-like immunoreactivity (FLI) in the paraventricular (PVN), periventricular (PEV) and supraoptic (SON) hypothalamic nuclei, and in the preoptic and retrochiasmatic regions, as early as 30 min after stimulation and up to 6 h, while these areas were mostly devoid of staining in isotonic saline-injected animals. The activation of the oxytocinergic system peaked at 30 min and declined at different rates in the PVN and in the SON after 90 min. The maximal percentage of OXY neurons expressing FLI upon osmotic stress was about 80% in the SON, PEV and LSN, 60% in the PVN and 50% in the medial preoptic area. Activated OXY neurons were found in both the magnocellular and parvocellular divisions of the system. These data show that OXY nuclei in the rat hypothalamus are differentially activated by osmotic stress. They also suggest a role of OXY in the central as well as in the humoral response to changes in plasma osmolarity.

Animals↗
PubMed1992

Cholinergically induced REM sleep triggers Fos-like immunoreactivity in dorsolateral pontine regions associated with REM sleep.

We sought to determine the presence of Fos-like immunoreactive (Fos-LI) cells in the pontine brainstem following cholinergically induced sustained rapid-eye movement (REMc) sleep in cats. Microinjections (0.25 microliter) of vehicle (N = 2) or carbachol (2.0 micrograms/0.25 microliter; N = 4) were made into the medial pontine reticular formation. Carbachol produced a state with all the signs of natural REM sleep and with durations of 15.2-57.8 min. Compared with vehicle control animals, carbachol treated animals showed a significantly higher number of Fos-LI cells in pontine regions implicated in REM sleep generation, with longer REMc bouts associated with more Fos-LI cells than the short-duration bout. Regions with REMc-associated Fos-LI increases included: the lateral dorsal tegmental (LDT) and pedunculopontine tegmental (PPT) nuclei, where some Fos-LI cells were immunohistochemically identified as cholinergic; the locus coeruleus, where some of the Fos-LI cells were identified to be catecholaminergic; the dorsal raphe and the pontine reticular formation. These findings suggest immediate early gene activation is associated with the ubiquitous biological state of REM sleep.

Acetylcholine↗
PubMed1992

c-Fos protein expression in the rat subfornical organ following osmotic stimulation.

To examine the role of the subfornical organ (SFO) in the osmotic activation of hypothalamic neurons, the responses of the SFO to osmotic stimulation were evaluated by using c-Fos protein immunohistochemistry. Numerous c-Fos-immunoreactive nuclei were found in the SFO of rats injected i.p. with hypertonic saline solution as early as 30 min after stimulation, and the effect lasted up to 3 h. Only a few c-Fos-positive cells were detected in the SFO of rats injected with isotonic saline. However, electrolytic lesions of the SFO did not prevent the osmotic activation of the hypothalamic paraventricular and supraoptic nuclei. These data suggest that the SFO and the hypothalamic magnocellular nuclei are simultaneously but separately activated by osmotic stress.

Animals↗
PubMed1992

Reversal of diabetes insipidus in Brattleboro rats: intrahypothalamic injection of vasopressin mRNA.

Messenger RNAs occur within the axons of magnocellular hypothalamic neurons known to secrete oxytocin and vasopressin. In Brattleboro rats, which have a genetic mutation that renders them incapable of vasopressin expression and secretion and thus causes diabetes insipidus, injection into the hypothalamus of purified mRNAs from normal rat hypothalami or of synthetic copies of the vasopressin mRNA leads to selective uptake, retrograde transport, and expression of vasopressin exclusively in the magnocellular neurons. Temporary reversal of their diabetes insipidus (for up to 5 days) can be observed within hours of the injection. Intra-axonal mRNAs may represent an additional category of chemical signals for neurons.

Animals↗
PubMed1992

Training neuroscientists for the 21st century.

Maintaining the highest possible level of talented researchers relies critically on the ability to recruit, train and retain the best young students to the neurosciences. This article addresses the need for trainers to look beyond technical skills, on which research training conventionally concentrates, to some para-scientific skills that may help assure survival during the apparently perennial periods of scarce resources.

Neurology↗
PubMed1992

Distribution and ontogeny of parvalbumin immunoreactivity in the chicken retina.

The distribution of parvalbumin-like immunoreactivity was studied in the embryonic and postnatal chicken retina. In post-hatched chickens, parvalbumin-like immunoreactivity was confined to amacrine cells. Three distinct subpopulations were identifiable based upon soma position and level of dendritic arborization in the inner plexiform layer. The primary dendrites from parvalbumin-immunoreactive amacrine cells descended vertically into the inner plexiform layer and eventually branched to give rise to a laminarly arrayed plexus in sublamina I, sublamina V and, to a lesser extent, at the boundary between sublaminae III and IV. Parvalbumin-like immunoreactive amacrine cells projecting to sublamina I of the inner plexiform layer were consistently monostratified. Some, but not all, contributed thick fibers to sublamina I that could be followed for long distances across the retina and were generally not radially organized. The parvalbumin-like immunoreactive cells that projected to sublamina V gave rise to a primary dendrite from which three to five fibers branched radially. Collateral branches of these same primary dendrites gave rise to the parvalbumin-like immunoreactive plexus at the interface between sublaminae III and IV. In prenatal chickens, parvalbumin-like immunoreactivity was not detected until embryonic day 14. At this time it appeared as a faint band at the inner nuclear layer-inner plexiform layer boundary in the central retina. By embryonic day 18 the intensity of immunoreactivity and the complexity of the arborizations of the parvalbumin-like immunoreactive dendrites approached that seen in the post-hatched chicken. In the chicken retina, parvalbumin-like immunoreactivity was displayed by morphologically distinct subpopulations of amacrine cells suggesting that these amacrine cells may subserve diverse functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Applications of DAPI cytochemistry to neurobiology.

4',6-Diamidino-2-phenylindole hydrochloride (DAPI) is a fluorescent dye with high affinity for DNA. We have employed it as a fluorescent chromatin counterstain on sections immunofluorescent-stained using rhodamine and on tissues enzymatically stained using beta-galactosidase. DAPI also allows easy identification of mitotic figures and can be used to supplement cytochemical studies involving cell division in the nervous system.

Animals↗
PubMed1991

Dibutyryl-cAMP induces SNAP-25 translocation into the neurites in PC12.

SNAP-25 immunoreactivity was translocated into the endings of the processes induced in PC12 cells by dibutyryl-cAMP-treatment. Conversely, the protein was not present in the endings of the processes seen after NGF-treatment unless dibutyryl-cAMP was used simultaneously. This redistribution of SNAP-25 immunoreactivity appeared to be dependent upon new protein synthesis. Finally, dibutyryl-cAMP was capable of inducing SNAP-25 expression.

Adrenal Gland Neoplasms↗
PubMed1991

Pituitary hyperplasia and gigantism in mice caused by a cholera toxin transgene.

Cyclic AMP is thought to act as an intracellular second messenger, mediating the physiological response of many cell types to extracellular signals. In the pituitary, growth hormone (GH)-producing cells (somatotrophs) proliferate and produce GH in response to hypothalamic GH-releasing factor, which binds a receptor that stimulates Gs protein activation of adenylyl cyclase. We have now determined whether somatotroph proliferation and GH production are stimulated by cAMP alone, or require concurrent, non-Gs-mediated induction of other regulatory molecules by designing a transgene to induce chronic supraphysiological concentrations of cAMP in somatotrophs. The rat GH promoter was used to express an intracellular form of cholera toxin, a non-cytotoxic and irreversible activator of Gs. Introduction of this transgene into mice caused gigantism, elevated serum GH levels, somatotroph proliferation and pituitary hyperplasia. These results support the direct triggering of these events by cAMP, and illustrate the utility of cholera toxin transgenes as a tool for physiological engineering.

Amino Acid Sequence↗