The E2F1-3 transcription factors are essential for cellular proliferation

The retinoblastoma tumour suppressor (Rb) pathway is believed to have a critical role in the control of cellular proliferation by regulating E2F activities. E2F1, E2F2 and E2F3 belong to a subclass of E2F factors thought to act as transcriptional activators important for progression through the G1/S transition. Here we show, by taking a conditional gene targeting approach, that the combined loss of these three E2F factors severely affects E2F target expression and completely abolishes the ability of mouse embryonic fibroblasts to enter S phase, progress through mitosis and proliferate. Loss of E2F function results in an elevation of p21Cip1 protein, leading to a decrease in cyclin-dependent kinase activity and Rb phosphorylation. These findings suggest a function for this subclass of E2F transcriptional activators in a positive feedback loop, through down-modulation of p21Cip1, that leads to the inactivation of Rb-dependent repression and S phase entry. By targeting the entire subclass of E2F transcriptional activators we provide direct genetic evidence for their essential role in cell cycle progression, proliferation and development.

Visceral afferent hypersensitivity in irritable bowel syndrome--evaluation by cerebral evoked potential after rectal stimulation

OBJECTIVES

Gut hypersensitivity has been shown to be present in irritable bowel syndrome. The current study sought to determine the involvement or hypersensitivity of the gut afferents, objectively, by recording cerebral evoked potential after rectal stimulation.

METHODS

In 13 patients with irritable bowel syndrome and nine healthy controls, rectal perception thresholds to electrical stimulation were measured, and cerebral evoked potentials were recorded from 2 cm behind vertex (Cz') after rectal stimulation electrically (frequency 1 Hz, duration 0.5 ms) at an intensity 50% above perception threshold and with filter setting 1-250 Hz.

RESULTS

Perception thresholds to rectal electrical stimuli in patients with irritable bowel syndrome were lower than controls (p < 0.05). Rectal stimulation led to recognizable and reproducible cerebral evoked potentials. P1, N1, P2 latencies in patients with irritable bowel syndrome were shorter than that in controls (p < 0.05). P1/N1 amplitude was greater in patients with irritable bowel syndrome than in controls (p < 0.05).

CONCLUSIONS

The shorter latency and increased amplitude of cerebral evoked potential after rectal stimulation in patients with irritable bowel syndrome compared to controls provide objective evidence supporting visceral afferent hypersensitivity as the underlying mechanism in irritable bowel syndrome.

Osteoblastoma of dorsal spine: a case report

A case of benign osteoblastoma affecting posterior element of spine with pain and paraplegia in a female is being presented with brief review of literature. Early diagnosis and surgical excision remains the mainstay of treatment.

Clinical profile of myasthenia gravis

Seventy three patients with myasthenia gravis were studied over 9 years period (1987-1995) in departments of neuromedicine, respiratory care unit, cardiothoracic unit of Institute of Postgraduate Medical Education and Research and Bangur Institute of Neurology, Calcutta, with reference to their clinical presentations, laboratory findings and various modes of treatment. Commonest age of presentation was 5th decade in men and 3rd decade in women. Fifty five percent of patients belong to type 2A myasthenia gravis (Osserman classification). Presentation was insidious (67.2%) and course was slowly progressive (65.7%) in majority of cases. Fatigability and ptosis were commonest clinical presentation and diurnal variation was noticed in 60% of cases. Edrophonium test was positive in 90.4% of cases and repetitive nerve stimulation showed 93.5% positivity in 30 cases. 27 patients (36.9%) underwent thymectomy and out of these, 89% of patients showed hyperplastic change and thymoma in 11% of cases. Mortality rate including both operated and nonoperated patients was recorded to be 9.6%. We observed earlier onset of myasthenia in male, higher incidence of oculo-bulbar involvement and lower incidence of respiratory problem and thymoma.

Pattern of motor neurone disease in eastern India

A clinical study about the pattern of motor neurone disease in eastern India was carried out from July 1993 to June 1995 at Bangur Institute of Neurology, Calcutta and SSKM Hospital, Calcutta. A total of 110 cases were studied and they constituted 0.11% of all neurological cases seen in the general OPD. Of 110 cases, amyotropic lateral sclerosis (ALS) constituted 43.6%, progressive muscular atrophy (PMA) 10.9%, post-polio progressive muscular atrophy (PPMA) 1.8%, spinal muscular atrophy (SMA) 20%, atypical form Madras pattern of MND (MMND) 0.9% and monomelic amyotrophy (MMA) 22.7% of cases. Disease is more common in males than females and average duration of symptoms before presentation varied from 1 to 12 months. Most of the patients were either agricultural labourers or manual workers in ALS variety whereas MMA variety was evenly distributed in both hard labourers and sedentary workers. Most of the patients in MMA and SMA groups presented before 30 years of age whereas ALS and PMA group presented after 30 years. Trauma was the commonest antecedent event in ALS and MMA followed by electrocution in the same two groups. Family history was found to be absent in SMA group though the disease is considered as a hereditary one. Weakness of the limbs and wasting of the muscles were common presenting symptoms and signs. Bulbar symptoms and signs were found only in the ALS group. EMG showed neurogenic pattern and mixed pattern in most of the patients in all groups. Only a few patients showed myopathic pattern. Neuroimaging study helped in exclusion of compressive lesion excepting two cases of MMA where facetal hypertrophy was present. Monomelic amyotrophy, a special variety of motor neurone disease, is not rare in this part as compared to other parts of India and Asia.

Effect of stress on serotonin, norepinephrine, epinephrine and corticosterone contents in the soft-shelled turtle

1. Adult soft-shelled turtles were exposed to hyperosmotic and dehydration stresses. 2. Acute treatment for 0.5, 1 or 2 h with sodium chloride (3.6%, single intramuscular injection, 2 mL volume) caused depletion of pineal serotonin contents followed by elevation of norepinephrine and epinephrine levels. In addition, it depleted corticosterone and norepinephrine from the adrenal gland. 3. The serotonin level also decreased with a concomitant increase of 5-hydroxyindoleacetic acid but without any discernible change in catecholamine content after chronic treatment with sodium chloride (3.6%, 0.5 mL daily for 7 days). 4. Dehydration for 7 days brought about depletion of serotonin and epinephrine levels and elevation of norepinephrine level. 5. The findings suggest that hyperosmotic stress has a definite influence on pineal-paraphyseal serotonin, 5-hydroxyindoleacetic acid, norepinephrine and epinephrine concentrations, and adrenal corticosterone and norepinephrine contents in Lissemys turtles. Dehydration stress also modulates pineal-paraphyseal serotonin, norepinephrine and epinephrine concentrations.