Ascending spinal pathways for the somatosympathetic A and C reflexes.

Sympathetic unit nerve activity was recorded from the cervical sympathetic trunk of anesthetized, vagotomized, and carotid sinus-denervated cats. Single pulses or short trains of pulses with suprathreshold intensity for afferent C fibers were applied to the common peroneal nerve to elicit somatosympathetic A or simultaneous A and C reflexes, respectively. Bilateral lesions of an ascending spinal pathway in the dorsolateral sulcus area (DLS) of the T12 spinal cord eliminated the sympathetic C reflex. The remaining somatosympathetic A reflex was abolished by the subsequent lesion of an ascending spinal pathway in the dorsolateral funiculus (DLF) bilaterally. The duration of the silent period was found to be mainly influenced by an ascending spinal pathway in the DLF. It was concluded that excitation of afferent A fibers activates ascending pathways mainly in the DLF and a smaller contribution in the DLS of the spinal cord. This produces a small reflex excitation (A reflex) followed by a long silent period in the sympathetic nerves resulting in a net decrease of total sympathetic nerve activity. On the other hand, excitation of afferent C fibers activates the ascending spinal pathway in the DLS. This produces a reflex excitation (C reflex) which exceeds the decreased activity due to the silent period resulting in a net increase of total sympathetic nerve activity.     

Increased Sensitivity of Lymphocytes from Atopic Individuals to Histamine-Induced Suppression

Histamine depressed lymphocyte reactivity to phytohemagglutinin and, to a lesser degree, concanavalin A, when administered simultaneously with mitogen to lymphocyte cultures. Addition of histamine at later times to the cultures appeared to have a slightly enhancing effect on the lymphocyte response. Stimulation of lymphocytes with pokeweed mitogen was in some cases enhanced, even by high concentrations of histamine. Lymphocytes from atopic individuals were more sensitive to the inhibitory effect of histamine than lymphocytes from nonatopic individuals. The sensitivity appeared age-dependent, but within each age group histamine evoked significantly more suppression on lymphocytes from atopic than from nonatopic individuals. The possibility that the altered reactivity of lymphocytes to histamine, which appears to be associated with atopic allergy, is of pathogenic importance, is discussed, and a hypothesis for the development of atopic disease is proposed.     

Predominance of null mutations in ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity and cancer predisposition. The responsible gene, ATM, was recently identified by positional cloning and found to encode a putative 350 kDa protein with a Pl 3-kinase-like domain, presumably involved in mediating cell cycle arrest in response to radiation-induced DNA damage. The nature and location of A-T mutations should provide insight into the function of the ATM protein and the molecular basis of this pleiotropic disease. Of 44 A-T mutations identified by us to date, 39 (89%) are expected to inactivate the ATM protein by truncating it, by abolishing correct initiation or termination of translation, or by deleting large segments. Additional mutations are four smaller in-frame deletions and insertions, and one substitution of a highly conserved amino acid at the Pl 3-kinase domain. The emerging profile of mutations causing A-T is thus dominated by those expected to completely inactivate the ATM protein. ATM mutations with milder effects may result in phenotypes related, but not identical, to A-T.      

Responses of canine endocardium to stimulation of the upper thoracic roots

In each of 10 mongrel dogs anesthetized with alpha chloralose, strain-gauge arches were sutured to five epicardial and three endocardial locations. Comparisons of contractile force responses during stimulation of the left and right roots of the same segmental level revealed several differences dependent upon the particular myocardial area observed. Of the three left ventricular endocardial areas studied, the interventricular septum was the most responsive, particularly during stimulation of the right roots. The basal free wall and posterior papillary muscle were more responsive to left-root than to right-root stimulations. Epicardial responses were consistent with those previously reported. Generally, all areas responded to the greatest degree during stimulation of the second roots with the third and first next in order of effectiveness. Although stimulation of each level of preganglionic outflow activated all epicardial and endocardial segments of the myocardium, the magnitude of the changes in contractile force were highly variable dependent upon the specific level of preganglionic outflow and the location of the strain-gauge arch.     

Breast cancer detection: one versus two views

Mammographic examinations of 169 patients with 172 biopsy-proved carcinomas, and of 194 healthy subjects, were interpreted independently and retrospectively by three experienced mammographers, initially as single-view oblique examinations and 6 months later as two-view oblique-cephalocaudal examinations. For the single-view examinations of the cancer patients, 67% of the cancers were correctly recommended for biopsy, additional views were requested for 23%, and a "negative" interpretation was made for 10%. For the single-view examinations of healthy subjects, biopsy was recommended for 7% and additional views were recommended for 32%. For the two-view examinations of women with cancer, 80% of the cancers were correctly recommended for biopsy, additional views were requested for 4%, and a "negative" interpretation was made for 16%. For two-view examinations of healthy subjects, biopsy was recommended for 7% and additional views were requested for only 5%. The authors conclude that single-view screening should not be performed, because it would lead to an excessive number of "call-back" examinations of healthy patients, producing additional cost and anxiety that would outweigh any theoretical benefit.