Modulating the Excitability of Olfactory Output Neurons Affects Whole-Body Metabolism

Metabolic state can alter olfactory sensitivity, but it is unknown whether the activity of the olfactory bulb (OB) may fine tune metabolic homeostasis. Our objective was to use CRISPR gene editing in male and female mice to enhance the excitability of mitral/tufted projection neurons (M/TCs) of the OB to test for improved metabolic health. Ex vivo slice recordings of MCs in CRISPR mice confirmed increased excitability due the targeted loss of Kv1.3 channels, which resulted in a less negative resting membrane potential (RMP), enhanced action potential (AP) firing, and insensitivity to the selective channel blocker margatoxin (MgTx). CRISPR mice exhibited enhanced odor discrimination using a habituation/dishabituation paradigm. CRISPR mice were challenged for 25 weeks with a moderately high-fat (MHF) diet, and compared with littermate controls, male mice were resistance to diet-induced obesity (DIO). Female mice did not exhibit DIO. CRISPR male mice gained less body weight, accumulated less white adipose tissue, cleared a glucose challenge more quickly, and had less serum leptin and liver triglycerides. CRISPR male mice consumed equivalent calories as control littermates, and had unaltered energy expenditure (EE) and locomotor activity, but used more fats for metabolic substrate over that of carbohydrates. Counter to CRISPR-engineered mice, by using chemogenetics to decrease M/TC excitability in male mice, activation of inhibitory designer receptors exclusively activated by designer drugs (DREADDs) caused a decrease in odor discrimination, and resulted in a metabolic profile that was obesogenic, mice had reduced EE and oxygen consumption (VO2). We conclude that the activity of M/TC projection neurons canonically carries olfactory information and simultaneously can regulate whole-body metabolism.SIGNIFICANCE STATEMENT The olfactory system drives food choice, and olfactory sensitivity is strongly correlated to hunger and fullness. Olfactory function thereby influences nutritional balance and obesity outcomes. Obesity has become a health and financial crisis in America, shortening life expectancy and increasing the severity of associated illnesses. It is expected that 51% of Americans will be obese by the year 2030. Using CRISPR gene editing and chemogenetic approaches, we discovered that changing the excitability of output neurons in the olfactory bulb (OB) affects metabolism and body weight stabilization in mice. Our results suggest that long-term therapeutic targeting of OB activity to higher processing centers may be a future clinical treatment of obesity or type II Diabetes.

Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes

The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion.

Neuronal injury in experimental status epilepticus in the rat: role of acidosis

Systemic and cerebral acidosis accompanies generalized tonic-clonic seizures and status epilepticus. Acidosis during status may be modified by neuromuscular paralysis, intubation and ventilation, or administration of a base, but the effect of acidosis on neuronal injury from status is uncertain. We studied the effect of acidosis, induced by hypercarbic ventilation, on heat-shock protein (HSP72) induction in rat brain as a measure of neuronal injury in experimental status epilepticus. Acidosis was found to attenuate neuronal injury, independent of its anticonvulsant effect.

Expression of CD60 on multiple cell lineages in inflammatory synovitis

BACKGROUND

CD60 is a recently described T cell subset marker that is expressed on the surface of most T lymphocytes in synovial tissue and fluid and on a smaller proportion of peripheral T cells. Activation of T lymphocytes can be triggered through CD60. CD60 is also expressed by neuroectodermally derived cells in thymic epithelium and in skin.

EXPERIMENTAL DESIGN

Immunohistologic analysis of CD60 expression in synovium and thymus was performed using formalin-fixed tissue samples. Nonlymphoid cell lines grown from similar tissues were analyzed by flow cytometry.

RESULTS

CD60 was readily identified in formalin-fixed, paraffin-embedded tissues. Simultaneous examination of CD60 distribution and cell morphology demonstrated that, in addition to its presence on T cells, CD60 was also expressed by a variety of nonlymphoid cells in synovium, including synovial lining cells, vascular endothelium, and dendritic-appearing cells deep within synovial tissue. Synovial tissue expression of CD60 was similar in rheumatoid arthritis and in other forms of inflammatory arthritis. In addition, it was strongly expressed by giant cells in pigmented villonodular synovitis. Surface expression of CD60 was detected by flow cytometry on cultured synoviocytes and on other CD60+ nonlymphoid cells, thus excluding adsorption of CD60 shed by T cells as a sufficient explanation of the immunohistologic findings.

CONCLUSIONS

These results define the T cell-activating CD60 determinant as a broadly distributed Ag within synovial tissue, with a possible functional role in the activation of a variety of cellular populations. CD60 may also be a marker for previously undescribed cell subsets in the synovial compartment, possibly including a cell population of neuroectodermal origin.

Epileptic tolerance: prior seizures protect against seizure-induced neuronal injury

Heat shock proteins (HSPs) are induced by a variety of insults to the nervous system, including seizures, and may be neuroprotective. If this is so, prior induction of HSPs should decrease neuronal damage upon re-exposure to an injurious stimulus. To test this hypothesis in relation to seizures, bicuculline was given to rats in two sessions, separated by 1, 3, 5 or 7 days; seizure activity was recorded, and HSP-like immunoreactivity and neuronal injury (acid-fuchsin staining) were quantified in the CA3c sector of the hippocampus. Prior seizures conferred a time-dependent protective effect against hippocampal injury induced by subsequent seizures, which may represent 'epileptic tolerance', analogous to the previously described phenomenon of 'ischemic tolerance'.

Bilateral intranigral NMDA blockade increases status duration and neuronal injury from systemic kainic acid

Limbic seizures may be under the regulation of the substantia nigra, pars reticulata (SNpr). Using microinjection of the NMDA antagonist AP7, we investigated the role of SNpr in modulating seizures induced by kainic acid. Seizure severity was analyzed electrographically and neural injury assessed by measurement of heat shock protein (HSP) expression and acid fuchsin (AF) staining of vulnerable hippocampal cells. Intranigral injection of AP-7 increased the duration of electrographic seizure discharges and the number of HSP-positive and acid fuchsin stained cells in all hippocampal sectors, suggesting that blockade of the NMDA receptors in SNpr enhanced neural injury.

Experience with ciprofloxacin

The authors report results of a multicenter study of 65 patients treated with ciprofloxacin. Twenty infections were microbiologically proven; eradication of the pathogen was achieved in 80%.