Synapse-Specific Defects in Synaptic Transmission in the Cerebellum of W246G Mutant ELOVL4 Rats-a Model of Human SCA34

Elongation of very long fatty acids-4 (ELOVL4) mediates biosynthesis of very long chain-fatty acids (VLC-FA; ≥28 carbons). Various mutations in this enzyme result in spinocerebellar ataxia-34 (SCA34). We generated a rat model of human SCA34 by knock-in of a naturally occurring c.736T>G, p.W246G mutation in the Elovl4 gene. Our previous analysis of homozygous W246G mutant ELOVL4 rats (MUT) revealed early-onset gait disturbance and impaired synaptic transmission and plasticity at parallel fiber-Purkinje cell (PF-PC) and climbing fiber-Purkinje cell (CF-PC) synapses. However, the underlying mechanisms that caused these defects remained unknown. Here, we report detailed patch-clamp recordings from Purkinje cells that identify impaired synaptic mechanisms. Our results show that miniature EPSC (mEPSC) frequency is reduced in MUT rats with no change in mEPSC amplitude, suggesting a presynaptic defect of excitatory synaptic transmission on Purkinje cells. We also find alterations in inhibitory synaptic transmission as miniature IPSC (mIPSC) frequency and amplitude are increased in MUT Purkinje cells. Paired-pulse ratio is reduced at PF-PC synapses but increased at CF-PC synapses in MUT rats, which along with results from high-frequency stimulation suggest opposite changes in the release probability at these two synapses. In contrast, we identify exaggerated persistence of EPSC amplitude at CF-PC and PF-PC synapses in MUT cerebellum, suggesting a larger readily releasable pool (RRP) at both synapses. Furthermore, the dendritic spine density is reduced in MUT Purkinje cells. Thus, our results uncover novel mechanisms of action of VLC-FA at cerebellar synapses, and elucidate the synaptic dysfunction underlying SCA34 pathology.SIGNIFICANCE STATEMENT Very long chain-fatty acids (VLC-FA) are an understudied class of fatty acids that are present in the brain. They are critical for brain function as their deficiency caused by mutations in elongation of very long fatty acids-4 (ELOVL4), the enzyme that mediates their biosynthesis, results in neurologic diseases including spinocerebellar ataxia-34 (SCA34), neuroichthyosis, and Stargardt-like macular dystrophy. In this study, we investigated the synaptic defects present in a rat model of SCA34 and identified defects in presynaptic neurotransmitter release and dendritic spine density at synapses in the cerebellum, a brain region involved in motor coordination. These results advance our understanding of the synaptic mechanisms regulated by VLC-FA and describe the synaptic dysfunction that leads to motor incoordination in SCA34.

Ablation of Sphingosine Kinase 1 Protects Cornea from Neovascularization in a Mouse Corneal Injury Model

The purpose of this study was to investigate the role of sphingosine kinase 1 (SphK1), which generates sphingosine-1-phosphate (S1P), in corneal neovascularization (NV). Wild-type (WT) and Sphk1 knockout (Sphk1^−/−) mice received corneal alkali-burn treatment to induce corneal NV by placing a 2 mm round piece of Whatman No. 1 filter paper soaked in 1N NaOH on the center of the cornea for 20 s. Corneal sphingolipid species were extracted and identified using liquid chromatography/mass spectrometry (LC/MS). The total number of tip cells and those positive for ethynyl deoxy uridine (EdU) were quantified. Immunocytochemistry was done to examine whether pericytes were present on newly forming blood vessels. Cytokine signaling and angiogenic markers were compared between the two groups using multiplex assays. Data were analyzed using appropriate statistical tests. Here, we show that ablation of SphK1 can significantly reduce NV invasion in the cornea following injury. Corneal sphingolipid analysis showed that total levels of ceramides, monohexosyl ceramides (HexCer), and sphingomyelin were significantly elevated in Sphk^−/− corneas compared to WT corneas, with a comparable level of sphingosine among the two genotypes. The numbers of total and proliferating endothelial tip cells were also lower in the Sphk1^−/− corneas following injury. This study underscores the role of S1P in post-injury corneal NV and raises further questions about the roles played by ceramide, HexCer, and sphingomyelin in regulating corneal NV. Further studies are needed to unravel the role played by bioactive sphingolipids in maintenance of corneal transparency and clear vision.

Selective Ablation of Sod2 in Astrocytes Induces Sex-Specific Effects on Cognitive Function, d-Serine Availability, and Astrogliosis

Cognitive decline is a debilitating aspect of aging and neurodegenerative diseases such as Alzheimer's disease are closely associated with mitochondrial dysfunction, increased reactive oxygen species, neuroinflammation, and astrogliosis. This study investigated the effects of decreased mitochondrial antioxidant response specifically in astrocytes on cognitive performance and neuronal function in C57BL/6J mice using a tamoxifen-inducible astrocyte-specific knockout of manganese superoxide dismutase (aSOD2-KO), a mitochondrial matrix antioxidant that detoxifies superoxide generated during mitochondrial respiration. We reduced astrocyte SOD2 levels in male and female mice at 11-12 months of age and tested in an automated home cage (PhenoTyper) apparatus for diurnal patterns, spatial learning, and memory function at 15 months of age. aSOD2-KO impaired hippocampal-dependent spatial working memory and decreased cognitive flexibility in the reversal phase of the testing paradigm in males. Female aSOD2-KO showed no learning and memory deficits compared with age-matched controls despite significant reduction in hippocampal SOD2 expression. aSOD2-KO males further showed decreased hippocampal long-term potentiation, but paired-pulse facilitation was unaffected. Levels of d-serine, an NMDA receptor coagonist, were also reduced in aSOD2-KO mice, but female knockouts showed a compensatory increase in serine racemase expression. Furthermore, aSOD2-KO mice demonstrated increased density of astrocytes, indicative of astrogliosis, in the hippocampus compared with age-matched controls. These data demonstrate that reduction in mitochondrial antioxidant stress response in astrocytes recapitulates age-related deficits in cognitive function, d-serine availability, and astrogliosis. Therefore, improving astrocyte mitochondrial homeostasis may provide a therapeutic target for intervention for cognitive impairment in aging.SIGNIFICANCE STATEMENT Diminished antioxidant response is associated with increased astrogliosis in aging and in Alzheimer's disease. Manganese superoxide dismutase (SOD2) is an antioxidant in the mitochondrial matrix that detoxifies superoxide and maintains mitochondrial homeostasis. We show that astrocytic ablation of SOD2 impairs hippocampal-dependent plasticity in spatial working memory, reduces long-term potentiation of hippocampal neurons and levels of the neuromodulator d-serine, and increases astrogliosis, consistent with defects in advanced aging and Alzheimer's disease. Our data provide strong evidence for sex-specific effects of astrocytic SOD2 functions in age-related cognitive dysfunction.

Improved Fluorescent Signal in Expansion Microscopy Using Fluorescent Fab Fragment Secondary Antibodies

Expansion microscopy (ExM) is a microscopic imaging approach that can achieve super-resolution visualization of fluorescently labeled biological samples using conventional fluorescence microscopy. The method is based on embedding of a fluorescently labeled biological sample in a hydrogel matrix followed by the physical expansion of the specimen, which is then viewed using a conventional fluorescent microscope. Variations of the method can be used to visualize endogenously expressed fluorescent proteins, such as GFP, fluorescently tagged antibodies, nucleic acids, or other fluorescently tagged molecules. A significant challenge of the method is that the physical expansion of the specimen produces a concommitant reduction in fluorescence intensity, which can make imaging difficult. We describe an approach for amplifying fluorescence signal following expansion of immunolabeled tissue sections by applying fluorescently labeled Fab fragment secondary antibodies to intensify fluorescent signal and enhance detection of labeling using conventional fluorescent microscopy.

A method to increase immunofluorescence signal intensity of Expansion Microscopy specimens is described.

Method utilizes commercially available reagents.

Enhances ability to acquire useful images in expanded tissue samples.

W246G Mutant ELOVL4 Impairs Synaptic Plasticity in Parallel and Climbing Fibers and Causes Motor Defects in a Rat Model of SCA34

Spinocerebellar ataxia (SCA) is a neurodegenerative disorder characterized by ataxia and cerebellar atrophy. A number of different mutations gives rise to different types of SCA with characteristic ages of onset, symptomatology, and rates of progression. SCA type 34 (SCA34) is caused by mutations in ELOVL4 (ELOngation of Very Long-chain fatty acids 4), a fatty acid elongase essential for biosynthesis of Very Long Chain Saturated and Polyunsaturated Fatty Acids (VLC-SFA and VLC-PUFA, resp., ≥28 carbons), which have important functions in the brain, skin, retina, Meibomian glands, testes, and sperm. We generated a rat model of SCA34 by knock-in of the SCA34-causing 736T>G (p.W246G) ELOVL4 mutation. Rats carrying the mutation developed impaired motor deficits by 2 months of age. To understand the mechanism of these motor deficits, we performed electrophysiological studies using cerebellar slices from rats homozygous for W246G mutant ELOVL4 and found marked reduction of long-term potentiation at parallel fiber synapses and long-term depression at climbing fiber synapses onto Purkinje cells. Neuroanatomical analysis of the cerebellum showed normal cytoarchitectural organization with no evidence of degeneration out to 6 months of age. These results point to ELOVL4 as essential for motor function and cerebellar synaptic plasticity. The results further suggest that ataxia in SCA34 patients may arise from a primary impairment of synaptic plasticity and cerebellar network desynchronization before onset of neurodegeneration and progression of the disease at a later age.

Sphingosine Kinase-1 Is Essential for Maintaining External/Outer Limiting Membrane and Associated Adherens Junctions in the Aging Retina

Sphingosine-1-phosphate (S1P) produced by sphingosine kinases (SPHK1 and SPHK2) is a signaling molecule involved in cell proliferation and formation of cellular junctions. In this study, we characterized the retinas of Sphk1 knockout (KO) mice by electron microscopy and immunocytochemistry. We also tested cultured Müller glia for their response to S1P. We found that S1P plays an important role in retinal and retinal pigment epithelial (RPE) structural integrity in aging mice. Ultrastructural analysis of Sphk1 KO mouse retinas aged to 15 months or raised with moderate light stress revealed a degenerated outer limiting membrane (OLM). This membrane is formed by adherens junctions between neighboring Müller glia and photoreceptor cells. We also show that Sphk1 KO mice have reduced retinal function in mice raised with moderate light stress. In vitro assays revealed that exogenous S1P modulated cytoskeletal rearrangement and increased N-cadherin production in human Müller glia cells. Aged mice also had morphological degeneration of the RPE, as well as increased lipid storage vacuoles and undigested phagosomes reminiscent of RPE in age-related macular degeneration. These findings show that SPHK1 and S1P play a vital role in the structural maintenance of the mammalian retina and retinal pigmented epithelium by supporting the formation of adherens junctions.

Distribution of ELOVL4 in the Developing and Adult Mouse Brain

ELOngation of Very Long chain fatty acids (ELOVL)-4 is essential for the synthesis of very long chain-fatty acids (fatty acids with chain lengths ≥ 28 carbons). The functions of ELOVL4 and its very long-chain fatty acid products are poorly understood at present. However, mutations in ELOVL4 cause neurodevelopmental or neurodegenerative diseases that vary according to the mutation and inheritance pattern. Heterozygous inheritance of different ELOVL4 mutations causes Stargardt-like Macular Dystrophy or Spinocerebellar Ataxia type 34. Homozygous inheritance of ELOVL4 mutations causes more severe disease characterized by seizures, intellectual disability, ichthyosis, and premature death. To better understand ELOVL4 and very long chain fatty acid function in the brain, we examined ELOVL4 expression in the mouse brain between embryonic day 18 and postnatal day 60 by immunolabeling using ELOVL4 and other marker antibodies. ELOVL4 was widely expressed in a region- and cell type-specific manner, and was restricted to cell bodies, consistent with its known localization to endoplasmic reticulum. ELOVL4 labeling was most prominent in gray matter, although labeling also was present in some cells located in white matter. ELOVL4 was widely expressed in the developing brain by embryonic day 18 and was especially pronounced in regions underlying the lateral ventricles and other neurogenic regions. The basal ganglia in particular showed intense ELOVL4 labeling at this stage. In the postnatal brain, cerebral cortex, hippocampus, cerebellum, thalamus, hypothalamus, midbrain, pons, and medulla all showed prominent ELOVL4 labeling, although ELOVL4 distribution was not uniform across all cells or subnuclei within these regions. In contrast, the basal ganglia showed little ELOVL4 labeling in the postnatal brain. Double labeling studies showed that ELOVL4 was primarily expressed by neurons, although presumptive oligodendrocytes located in white matter tracts also showed labeling. Little or no ELOVL4 labeling was present in astrocytes or radial glial cells. These findings suggest that ELOVL4 and its very long chain fatty acid products are important in many parts of the brain and that they are particularly associated with neuronal function. Specific roles for ELOVL4 and its products in oligodendrocytes and myelin and in cellular proliferation, especially during development, are possible.

Greater occipital nerve blockade for cluster headache

Cluster headache is perhaps the most painful of the primary headache disorders. Its treatment includes acute, transitional, and preventive therapy. Despite the availability of many treatments, cluster headache patients can still be difficult to treat. We treated 14 cluster headache patients with greater occipital nerve block as transitional therapy (treatment initiated at the same time as preventive therapy). The mean number of headache-free days was 13.1 + 23.6. Four patients (28.5%) had a good response, five (35.7%) a moderate, and five (35.7%) no response. The greater occipital nerve block was well tolerated with no adverse events. Headache intensity, frequency and duration were significantly decreased comparing the week before with the week after the nerve block (P < 0.003, P = 0.003, P < 0.005, respectively). Greater occipital nerve blockade is a therapeutic option for the transitional treatment of cluster headache.

Remitting form of hemicrania continua with seasonal pattern

Hemicrania continua is a primary headache syndrome characterized by a continuous, unilateral headache that is completely responsive to indomethacin. Hemicrania continua exists in continuous and remitting forms. Ten cases of the remitting form have been reported, none of which have had a seasonal pattern. We report a patient with remitting hemicrania continua with a clear seasonal predilection.

Influence of vertical vibration on heart rate of pigs

Pigs with a body weight between 15 and 20 kg were vibrated in the vertical direction for 1 h at 2, 8, and 18 Hz, in combination with root mean square (RMS) acceleration magnitudes of 1 or 3 m/s2. Welfare and stress were quantified by comparing heart rate characteristics during a control period (2200 to 0600) before vibration exposure and during vibration (1000 to 1100). The level of maximum heart rate and number of ventricular ectopic beats during vibration at 2 and 8 Hz in combination with a RMS acceleration of 3 m/s2 indicated a larger fear response than at 1 m/s2. Isocomfort contours based on mean heart rate during vibration showed the greatest specific sensitivity of the pigs to vibration at a frequency of 8 and 18 Hz, especially in combination with a RMS acceleration of 3 m/s2. During transport, RMS acceleration should be less than 3 m/s2 to protect pigs' welfare. Pigs were more sensitive to acceleration than to frequencies within the range of treatments in this investigation. Although the response of the pigs in this experiment fit within the model concept for adult humans and for domestic fowl, changes in heart rate are dependent on body weight.

Resonant frequencies of standing humans

Many forms of industrial illness are thought to result from the effects of vibration on the human body. Prolonged exposure causes undue stress and discomfort. At the human whole-body resonant frequency there is maximum displacement between the organs and the skeletal structure and thus this is one frequency of vibration that should be minimized in the workplace and elsewhere. The vertical whole-body resonant frequencies of 113 fully-clothed standing humans were measured using a vibrating beam method, which imposed a very low acceleration magnitude at the subjects' feet. The overall range of resonant frequencies was found to be from 9 to 16 Hz and independent of mass, height and mass to height ratio. The mean values (+/-1 s.e.) were 12.2 +/- 0.1 Hz for males and 12.8 +/- 0.2 Hz for females with an overall mean population value of 12.3 +/- 0.1 Hz.

Effects of physician prompters on long-term screening test behaviors

BACKGROUND

This study examines the long term effects of a prompter directed at a single screening test on the performance of preventive tests 12 to 24 months later.

METHODS

A retrospective chart review was performed that compared 114 patients who had a Papanicolau (Pap) smear prompter placed on their charts in 1990 with 86 patients who did not have a prompter placed. Chart audits determined if a Pap smear, breast examination, mammogram, rectal examination, stool occult blood, or serum cholesterol determination was performed 12 to 24 months after the prompter had been placed.

RESULTS

In the patient population that received prompters more than one year earlier, a significant increase was observed in Pap smears (40% vs 24%, p = 0.05), breast examinations (37% vs 20%, p = 0.009), and digital rectal examinations in patients 50 years of age and older (20% vs 0%).

CONCLUSIONS

When a prompter is placed on a chart to change physician behavior, a lasting effect is seen over one year later. However, increased screening is only observed in patients who initially had prompters placed on their charts. This may indicate that this change in screening behaviors is due to alterations in patient and not physician behaviors.

The Papanicolaou smear as a sentinel screening test for health screening in women

BACKGROUND

There has been evidence that, in primary care practices, health screening tests are not ordered in random fashion but instead are coupled or bundled into distinct groups. This study was performed to determine if the Papanicolaou (Pap) smear serves as a marker for other health screening tests.

METHODS

The study consisted of a retrospective chart review of female patients over the age of 18 years at three rural health clinics, followed by a prospective study of patients during a 3-month period in five rural family practice clinics. The study focused on whether a Pap smear was performed and whether a breast examination, mammogram, rectal examination or stool occult blood test, or serum cholesterol testing was performed.

RESULTS

In both the retrospective and prospective series, patients who received Pap smears were significantly more likely to receive breast examinations, mammograms, colorectal screening and cholesterol tests. In addition, the coupling of other screening tests with the Pap smear appeared to increase with advancing patient age, with a decline after age 70 years. In patients who did not have Pap smears, only cholesterol testing increased as patients aged.

CONCLUSION

Health screening tests in women are associated with the performance of a Pap smear. Providers may use the Pap smear as a marker of whether a woman has received screening for several other medical problems. Thus, the Pap smear can be considered a "sentinel" test for health screening in women, and efforts to identify women at high risk and increase health promotion and disease prevention in this group should focus on women who have not received this test.

Pulmonary histoplasmosis. A possible risk in people who cut decayed wood

We report three unrelated outbreaks of acute pulmonary histoplasmosis associated with cutting and gathering firewood in Minnesota. Clinical symptoms and laboratory findings from nine patients are reported. All recovered without treatment. This report emphasizes that physicians must consider cutting and gathering wood, especially decayed wood, as a potential risk for acute pulmonary histoplasmosis even in areas of the country where histoplasmosis is not considered prevalent.