Conduction properties of spinal cord axons in the myelin-deficient rat mutant.

Spinal cords of myelin-deficient and normal age-matched (control) rats were removed and their conduction and pharmacological properties studied in an in vitro brain slice chamber. The conduction velocity of the myelin-deficient dorsal column axons was reduced to about 25% of control axons; however, the amyelinated myelin-deficient axons displayed refractory periods and the ability to sustain high-frequency action potential discharge similar to that of dorsal column axons in control rats. Pharmacological results suggest that the myelin-deficient dorsal column axons qualitatively express a normal complement of ion channels and receptors. The demonstration of a normal representation of channels and receptors on these axons supports the proposal that the oligodendrocyte, and not the axon, is the site of the primary defect in the myelin-deficient rat mutant. It is concluded that, unlike acutely demyelinated axons which display marked frequency-dependent conduction block, amyelinated axons of the myelin-deficient rat spinal cord develop compensatory mechanisms to stabilize action potential conduction.     

Neurokinin A with K channel blockade potentiates contraction to electrical stimulation in human bronchus

This study investigated the effects of neurokinin A (NKA) on cholinergic neural responses in human bronchus. NKA (0.1 nM) did not alter the contractile response to submaximal electrical field stimulation. However, K⁺ channel blockade with 4-aminopyridine (4-AP) (0.1 mM) potentiated the response to electrical field stimulation (to 182 ± 25% of control, n = 4, P < 0.05) and subsequent addition of NKA in the presence of 4-AP produced further potentiation (to 123 ± 6% of the response to 4-AP n = 4, P < 0.05). Neither 4-AP (0.01 or 0.1 mM) nor NKA in the presence of 4-AP potentiated the actions of exogenous acetylcholine but in these experiments 4-AP itself produced a marked direct contractile response. Thus NKA in the presence of K⁺ channel blockade potentiates cholinergic neural response in human bronchus and this occurs at a prejunctional site.     

Spinal cord compression by spontaneous spinal subdural haematoma in polycythemia vera.

A woman with an eight-year history of polycythemia vera presented with numbness and weakness of both legs. A large spinal haematoma was revealed on magnetic resonance imaging which was treated clinically and which subsequently resolved.     

Psychotic symptoms and age of onset in affective disorders.

Prevalence of hallucinations and delusions was studied in 1,763 patients with unipolar major depression, bipolar affective disorder, and schizoaffective disorder. The authors found that the presence of psychotic features was negatively associated with age of onset for the group as a whole, and bipolar affective disorder (manic or mixed type) specifically. The clinical implications of the findings are discussed.     

High resolution computed tomography as a predictor of lung histology in systemic sclerosis

Background The relative proportions of fibrosis and inflammation seen by open lung biopsy examination is a predictor of disease outcome in fibrosing alveolitis. This study was designed to assess the ability of high resolution computed tomography to predict the histological appearance of open lung biopsy specimens from patients with systemic sclerosis.     

Prevalence of acne rosacea in a rheumatic skin disease subspecialty clinic.

There are many causes of malar erythema besides the classic butterfly rash of acute cutaneous lupus erythematosus (LE). Twenty-one patients (6.7% of new patient visits) referred to a dermatology department-based rheumatic skin disease subspecialty clinic over a 5-year period in whom a diagnosis of cutaneous LE had been entertained were found to have diagnoses other than autoimmune connective tissue diseases. Sixteen of the patients in this cohort (76%) had acne rosacea (rosacea), while the remaining five had other dermatologic disorders. Review of their records revealed that upon referral nine of these 21 patients (43%) had positive antinuclear antibody (ANA) assays, most with insignificant or marginal titers by our laboratory standards. On repeat ANA testing in our laboratory, all of these patients had insignificant ANA titers. Physicians may be giving too much weight to low-titer ANAs in assessing patients with isolated malar erythema. These issues are discussed in the overall context of the differential diagnosis of malar erythema. A simple punch skin biopsy can be very helpful in distinguishing cutaneous LE from other causes of malar erythema.