DTI of the Olfactory Bulb in COVID-19-Related Anosmia: A Pilot Study

This study aimed to assess the utility of DTI in the detection of olfactory bulb dysfunction in COVID-19-related anosmia. It was performed in 62 patients with COVID-19-related anosmia and 23 controls. The mean diffusivity and fractional anisotropy were calculated by 2 readers. The difference between the fractional anisotropy and mean diffusivity values of anosmic and control olfactory bulbs was statistically significant (P = .001). The threshold of fractional anisotropy and mean diffusivity to differentiate a diseased from normal olfactory bulb were 0.22 and 1.5, with sensitivities of 84.4% and 96.8%, respectively, and a specificity of 100%.

Clinical Significance of ALK-1 Gene Abnormalities in Diffuse Large Cell Lymphoma

Objectives

To detect relative frequency of anaplastic lymphoma kinase (ALK-1) gene abnormality in diffuse large cell lymphoma (DLCL) using fluorescence in situ hybridization (FISH), and correlate its presence with clinicopathological features which may be useful for choice of therapy and predict survival in newly diagnosed cases.

Patients and methods

A prospective study was done between March 2004 and October 2009. Fifty patients newly diagnosed with DLCL were enrolled into the study. Immunophenotyping was done and detection of ALK-1 gene abnormalities were carried out by immunohistochemically (IHC) and FISH. Patients that proved to be ALK-1 positive were treated with standard cyclophosphamide –hydroxy-daunorubicin- oncovin-prednisone (CHOP) protocol.

Results

All ALK +ve patients achieved complete remission (CR) vs. 93.5% CR and 6.5% partial remission (PR) for ALK −ve patients respectively. Disease free survival (DFS) at 24 months was 81.8% in the CHOP-14 group (ALK-1⁻) vs. 100% for the CHOP-21 group (ALK-1⁺). Overall survival (OS) at 30 months was 80.4% in the CHOP-14 group vs. 100% for the CHOP-21 group.

Effect of the GABA-transaminase inhibitor vigabatrin on exploratory behaviour in socially isolated rats

Elevation of the brain levels of the major inhibitory neurotransmitter gamma-aminobutyric acid (GABA) by inhibiting the GABA-catabolizing enzyme GABA-transaminase (GABA-T) is known to induce a number of functional effects including changes in behaviour. Vigabatrin (gamma-vinyl GABA, GVG) is an anti-epileptic drug that increases brain GABA levels by an irreversible inhibition of GABA-T. Using the elevated plus-maze model of anxiety and the open-field behaviour test, the effects of GABA-T inhibition and social isolation on rat exploratory behaviour were investigated. Social isolation for 1 week did not induce any change in the exploratory-behaviour of adult rats. However, rats socially isolated for 2 weeks, showed suppressed exploratory behaviour in the elevated plus-maze test. In both groups of differentially housed rats, treatment with vigabatrin at a dose of 250 mg/kg, i.p., significantly reduced the anxiety level in the plus-maze test. In the open-field test, vigabatrin tended to increase the exploratory behaviour only in the group of isolated rats. The results may suggest that vigabatrin has a better anxiolytic-like effect in the isolated rats than that in the socially housed rats.

Platelet and brain GABA-transaminase and monoamine oxidase activities in patients with complex partial seizures

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO-A and -B) were measured in blood platelets from 27 patients and hippocampal tissues from eight (GABA-T) and ten (MAO) patients with complex partial seizures. The activity of platelet GABA-T was found to be higher in the epileptic patients (43.37 +/- 13.53 pmol/min/mg protein, P < 0.005) in comparison with that found in 14 healthy volunteer subjects (29.59 +/- 13.14 pmol/min/mg protein). This difference was most pronounced in patients treated with carbamazepine (CBZ) (P < 0.01) and phenytoin (PHT) (P < 0.01). Contrary to the platelets, the activity of GABA-T in the hippocampi from the epileptic patients (6.937 +/- 2.204 nmol/min/mg protein) did not differ significantly from that found in seven non-epileptic control cases (7.158 +/- 0.951 nmol/min/mg protein). The increase in GABA-T activity in the blood platelets from the epileptic patients could not be explained by a direct effect of the antiepileptic compounds, since there were no changes in the activities on exposure to PHT, CBZ or VPA in vitro, either of blood platelets or of brain tissue. With regard to platelet MAO, no difference in the activity was found between the two groups, whereas the MAO-B activity in the hippocampi was significantly higher in the epileptic patients (3.51 +/- 1.32 nmol/mg/mg protein) than in the control cases (1.21 +/- 0.73 nmol/mg/mg protein) (P < 0.0004). There was no difference in MAO-A activity in the hippocampi between epileptic patients and controls.

CONCLUSION

In the hippocampi from patients with complex partial seizures the activities of the mitochondrial enzymes GABA-T and MAO-A were similar to those found in control subjects. The activity of MAO-B, however, was significantly higher indicating that there is an increased proportion of reactive astrocytes in epileptic hippocampus.

Anxiolytic-like effect of the GABA-transaminase inhibitor vigabatrin (gamma-vinyl GABA) on rat exploratory activity

Vigabatrin (gamma-vinyl GABA, GVG) is an irreversible inhibitor of GABA-transaminase (GABA-T). This study addressed the question of whether or not the inhibition of GABA-T has an anxiolytic effect in rats. Diazepam (1.5 mg/kg) and GVG (50 and 500 mg/kg) increased the tendency of rats to explore in the elevated plus-maze test, whereas the effect of general locomotor activity was diminished. The sedative effect of GVG (500 mg/kg) was more pronounced 6 h than 2 h after IP administration. The present findings suggest that even a partial inhibition of GABA-T results in a reduction of anxiety measures in a novel environment.

Effects of chronic treatment with the GABA-transaminase inhibitor vigabatrin on exploratory behaviour in rats

Vigabatrin (gamma-vinyl GABA, GVG) is an irreversible inhibitor of the enzyme GABA-transaminase (GABA-T) GABA-T is the enzyme responsible for the catabolism of the major inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the mammalian brain. Previously, a single administration of vigabatrin at a dose of 50 mg/kg was found to produce an anxiolytic-like effect on exploratory behaviour in rats and a decrease in the locomotor activity, 2 and 4 h after the injection and, presently, 24 h after the injection. Using an elevated plus-maze and open field tests, we investigated whether or not chronic administration of vigabatrin at the same dose (50 mg/kg/day, i.p.) for 14 and 28 days induces tolerance with regard to these effects. The anxiolytic-like effect of vigabatrin was found to persist in the elevated plus-maze test, as was the case with diazepam (5 mg/kg/day, i.p.), 24 h after the last injection. However, in the plus-maze and open field tests, the effects of vigabatrin and diazepam on the general locomotor activity were not found to be decreased.

Increase in brain GABA-transaminase activity after chronic ethanol treatment in rats

The activity of gamma-aminobutyrate aminotransferase (GABA-T) was measured in the brains of rats treated both acutely and sub-chronically with ethanol. Previously, chronic treatment with ethanol for 90 weeks was found to increase the mean brain GABA-T activity by 20-45%. In the present study acute ethanol treatment (4 g/kg, i.p.) did not induce and change in the activity of brain GABA-T with the exception of a small increase in the cerebellum (8%) and, after repeated treatment with ethanol (4 g/kg/day, i.p.) for one and two weeks, no change in the activity of GABA-T was also found in any of the brain regions examined. Subchronic treatment with ethanol for 14 weeks, performed according to two different schedules involving a voluntary intake of ethanol in the drinking water, resulted in approximately a two-fold difference in ethanol intake. A mean increase of 50-85% in the activity of GABA-T was found in all the brain regions of rats with higher ethanol intake in comparison with the group of rats with lower ethanol intake. A bimodal distribution of brain GABA-T activity, however, was found in the ethanol-treated rats, with 60% of the rats having a two-fold increase and the remaining 40% having unchanged activities. The addition of pyridoxal phosphate to the incubation media increased the activity of brain mitochondria from ethanol-treated rats with high brain GABA-T, whereas there was a decrease in the activity in control rats and in ethanol-treated rats in which no increase in brain GABA-T had occurred. These results show firstly, that in a subpopulation of rats, subchronically treated with ethanol for 14 weeks, there was a two-fold increase in brain GABA-T activity, while in another subgroup no change occurred, and, secondly, that this increase in GABA-T activity was a consequence of a change in the response of the apoprotein to the addition of the cofactor pyridoxal phosphate.

Brain GABA-transaminase and monoamine oxidase after chronic ethanol treatment in rats

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO-A and -B) were estimated in various brain regions of rats exposed to ethanol for 90 weeks. During the first period (weeks 1-58), the rats had access to both ethanol (10% w/v) and water during a 24-hr interval at the end of each week. At this point, the animals were given either a saline injection (intraperitoneally, group 1) or an ethanol injection (2.0 g/kg ip, group 2). During the second period (weeks 59-90), the rats in groups 1 and 2 had continuous access to both ethanol and water. The third group was composed of untreated control rats. Compared with controls, there was an increase of 20-45% in the mean brain GABA-T activity in both groups of ethanol-treated rats. However, analysis of the data for the individual ethanol-treated rats revealed a considerable difference in brain GABA-T activity. Thus, approximately 30% of the ethanol-treated rats showed approximately twice the activity of rats in the exposed groups and in the control group. There was no connection between ethanol intake, water intake, or body weight and GABA-T activity in any of the brain regions examined. There was no effect of ethanol in vitro on the activity of GABA-T in the brain cortex in concentrations of 20-100 mM, whereas acetaldehyde inhibited the activity by 15% at these concentrations. The present results suggest that there is a bimodal distribution with respect to the effect of ethanol on rat brain GABA-T activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Low platelet gamma-aminobutyrate aminotransferase and monoamine oxidase activities in chronic alcoholic patients

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO) were estimated in blood platelets from 25 male chronic alcoholics and from 27 healthy male volunteers without histories of alcohol abuse. Based on clinical criteria, the alcoholics were classified into type 1 or type 2 alcoholism. The activity of GABA-T was found to be lower both in type 1 and type 2 alcoholics than in healthy volunteers. With regard to MAO, the platelet activity was found to be significantly lower only in type 2 alcoholics in concordance with previous reports. No significant correlation was found between the activities of GABA-T and MAO in the blood platelets of healthy volunteers. The inhibitory effect of 400 mM ethanol on the platelet MAO activity increased with decreasing concentrations of the substrate phenylethylamine. The degree of inhibition of ethanol on the platelet MAO activity, however, did not differ significantly between alcoholics and controls.

Gamma-aminobutyrate aminotransferase activity in brains of schizophrenic patients

The activity of gamma-aminobutyrate aminotransferase (GABA-T) was estimated in twelve regions of brains from 22 control subjects and 6 cases with schizophrenia. In the controls, no significant correlation was found between the enzyme activity and age or postmortem interval (PMI) in any of the brain regions studied. In experiments on rat brains, the enzyme activity decreased about 20% during the first 2 hours of storage at room temperature and at 4 degrees C but remained steady thereafter. A similar initial decline in activity in the human brain material cannot be excluded. In the human brains, a slightly lower activity was found in the group below 75 years (n = 8) when compared with the group above 75 years (n = 8). A tendency to higher activities was found in female brains (n = 10) compared with male brains (n = 12). No significant difference in the enzyme activity was found between schizophrenic brains, in any of the regions studied, when compared to controls, matched for age, sex and PMI.

Brain gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO) in patients with Alzheimer's disease

Activities of Gamma-aminobutyrate aminotransferase (GABA-T) and Monoamine oxidase (MAO)-A and -B were estimated in postmortem brains from 6 control subjects without psychiatric or neurologic disorders and 8 histopathologically verified cases of patients with Alzheimer's disease and senile dementia of Alzheimer type (AD/SDAT). The enzyme activities were examined in four cortical brain regions, three nuclei in the basal ganglia, thalamus and white matter. GABA-T activities in the cortical regions (frontal, parietal, occipital and temporal cortices) and nucleus caudatus were significantly lowered in the AD/SDAT patients. The MAO-A activities were significantly increased in the occipital cortex, caudate nucleus, thalamus and white matter in the AD/SDAT patients. No significant differences were found in the other regions (frontal cortex, parietal cortex, temporal cortex, putamen and globus pallidus). The MAO-B activities in three cortical regions (frontal, parietal and occipital cortices), thalamus and white matter were significantly increased in the AD/SDAT patients, whereas no difference was apparent in the other regions. The changed activities could not be correlated with age or postmortem time. The present results are the first describing decreased GABA-T activities as well as increased MAO-A activities in brain from patients with AD/SDAT, while the results with MAO-B support previous findings. A possible connection was found between the order of magnitude of the changes in enzyme activities and the severity of the disease.

Studies on gamma-aminobutyrate aminotransferase (GABA-T) activities in human and rodent brain homogenates

Differences in the kinetic properties of brain gamma-aminobutyrate aminotransferase (GABA-transaminase; GABA-T) in different species are described in the present investigation. In both rat and human brain enzymes, the effect of temperature on the activity was studied. The maximal activity, for a 30-min incubation period, was attained at an incubation temperature of 45 degrees C for rat and 56 degrees C for human brain tissue. The addition of plasma or plasma proteins was found to induce a two-fold increase of the activity of rat brain GABA-T, whereas a slight inhibitory effect on human brain enzyme and no effect on mouse brain enzyme was observed. The species differences are shown to be the results of differences in the binding of the cofactor pyridoxal phosphate to the apoprotein, which are revealed when the free concentration of pyridoxal phosphate is reduced by binding to serum albumin.

GABA-transaminase activity in rat and human brain: regional, age and sex-related differences

The activity of 4-aminobutyrate:2-oxoglutarate transaminase (GABA-T) has been investigated in the rat and human brain. Both rat and human brain GABA-T retained its full activity for at least 2 months and with a loss of less than 10% after 6 months when frozen at -20 degrees C as tissue parts. There was a loss of activity of mouse brain GABA-T of about 15% per 24 hours postmortem. In the rat brain, GABA-T activity varied from low values in cortex and hippocampus to high in brain stem and cerebellum. There was a significant increase of GABA-T activity with age from 1 to 6 weeks and a significant reduction of the activity with age thereafter. Male rats had significant higher activity than female rats. In the human brain, GABA-T activities were measured in twelve regions of autopsied brains from 10 adult control subjects. No difference was found between the activities in the left and right sides. There is considerable variation in enzyme activity across the brain, with low activities in e.g. pons and medulla oblongata and high activities in e.g. caudatus, substantia nigra and hypothalamus. The activity of the enzyme is significantly different both between brain regions and between individuals.

Brain gamma-aminobutyrate transaminase and monoamine oxidase activities in suicide victims

The activity of gamma-aminobutyrate amino-transferase (GABA-T) and monoamine oxidase (MAO-A and -B) was measured in 42 postmortem human brains. Three brain regions (frontal cortex, cingulate cortex and hypothalamus) from 23 controls without known neurological or psychiatric disorder and from 19 suicide victims were analysed. The suicide victims were classified according to the use of violent and non-violent methods and to the presence or absence of a known history of depressive disorder. No difference was found between the series of suicide victims and the control subjects with regard to GABA-T activity. Carbon monoxide poisoning and death by drug overdose, however, were found to reduce the activity. The MAO-B activity did not differ between the groups. With MAO-A, however, a significant elevation (t = 2.01; P less than 0.05) was found in the hypothalamic region of the suicide victims. The difference seemed to be confined to the subgroup of suicides with a record of depressive disorder.