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Biomedical subjects

B H Smith

Publications and source records attributed to B H Smith.

At least 19 recordsLinked to original sources
PubMed1991

Conditional withholding of proboscis extension in honeybees (Apis mellifera) during discriminative punishment.

Proboscis extension conditioning of honeybee workers was used to test the ability of bees to respond to appetitive and aversive stimuli while restrained in a harness that allows subjects to move their antennae and mouthparts (Kuwabara, 1957; Menzel, Erber, & Masuhr, 1974). Subjects were conditioned to discriminate between two odors, one associated with sucrose feeding and the other associated with a 10 V AC shock if they responded to the sucrose unconditioned stimulus (US) in the context of that odor. Most Ss readily learned to respond to the odor followed by sucrose feeding and not to the odor associated with sucrose stimulation plus shock. Furthermore, in the context of the odor associated with shock, significantly more subjects withheld or delayed proboscis extension on stimulation with the sucrose US than they did in the context of the odor associated with feeding. Thus, restrained honeybees can readily learn to avoid shock according to an odor context by withholding proboscis extension to a normally powerful releaser. Analysis of individual learning curves revealed that subjects differed markedly in performance on this task. Some learn the discrimination quickly, whereas others show different kinds of response patterns.

Animals↗
PubMed1979

Growth-inhibitory effect of diphenylhydantoin on murine astrocytomas.

In previous work reported from this laboratory we found that diphenylhydantoin (DPH) inhibited the growth of 7 of 10 tissue-cultured human astrocytoma cell lines in a microtiter system. In this report we describe significant growth inhibition by DPH of two murine astrocytoma tissue cultures and correlate these in vitro findings with the in vivo activity of DPH in rat subcutaneous and intracranial tumor models. In the in vivo studies, rats were inoculated either subcutaneously or intracranially with RT9 or C6 rat gliomas. DPH or placebo was injected intraperitoneally in doses ranging from 50 to 150 mg/kg daily for 15 days. The DPH-treated rats showed significantly slower rates of tumor growth than untreated rats (p less than 0.01) in both the subcutaneous and intracranial models. At sacrifice, the tumor volume of the rats with subcutaneous tumors treated with DPH (100 mg/kg daily) was 62% less than the tumor volume of the control rats. Also, the number of "clonogenic" cells and thus, indirectly, the number of actively dividing tumor cells was 54% less in the intracranial tumors of the DPH-treated rats. These findings indicate that DPH may be a potentially useful adjunctive agent in the clinical chemotherapy of astrocytic tumors. Furthermore, the data presented indicate that in vitro test results are predictive for in vivo effects, supporting the idea that tissue culture can be used to screen for the effectiveness of clinically used chemotherapeutic agents.

Animals↗
PubMed1978

Malacoplakia of epididymis.

Malacoplakia localized to the epididymis is described. Ultrastructural study revealed the presence of bacterial bodies in phagolysosomes of malacoplakic macrophages. The possible role of the phagocytosed bacteria in the pathogenesis of malacoplakia is briefly discussed.

Aged↗
PubMed1977

McArdle's syndrome. Fine structural changes in muscle.

Two cases of McArdle's syndrome are reported. One is a "classical" example; the other is unusual because of the in vitro presence of muscle phosphorylase activity. In the latter case, the electronmicroscopic investigation confirmed the diagnosis. The fine structural changes characteristic of this disease are summarized and it is concluded that histochemical studies alone are insufficient to exclude the diagnosis of McArdl's myopathy.

Adult↗
PubMed1976

Electrotonic processing of information by brain cells.

In contrast to well-studied through-protection neurons that propagate information from one region to another in the central nervous system, short-axon or axonless neurons form local circuits, transmitting signals through synapses and electrical junctions between their dendrites. Interaction in this dendritic network proceeds without spike action potentials. Interaction is mediated by graded electrotonic changes of potential and is transmitted through high sensitivity (submillivolt threshold) synapses rather than by lower sensitivity (20 to 100-mv threshold) synapses typical of projection neurons. A crucial feature of local circuits is their high degree of interaction both through specialized junctional structures and through the extracellular fields generated by local and more distant brain regions. The anatomical evidence for the nature and distribution of neuronal local circuits in the nervous system is surveyed. Bioelectric mechanisms are discussed in relation to the special properties of local circuits, including dendrodendritic synapses, synaptic sensitivity, electrotonic coupling, and field effects. Intraneuronal and interneuronal transport of various types of substances suggests that the biochemical and the bioelectrical parameters are functionally interwoven. Through such interactions neuronal local circuits, with their distinctive properties, may play an essential role in higher brain function.

Action Potentials↗
PubMed1976

Hemangiopericytoma. An analysis of 106 cases.

A series of 106 cases of hemangiopericytoma was analyzed. The neoplasms occurred principally in adults (median age, 45 years), were deep seated, and were most common in the thigh (27 cases) and the pelvic retroperitoneum (26 cases). A painless mass was the first symptom in 96 of the patients. The median size of the excised tumors was 6.5 cm. Surgical removal of the tumor was often complicated by hemorrhage because of marked dilatation of the vascular bed in the vicinity of the neoplasm, probably as the result of rapid exchange of blood from the arterial to the venous circulation within the tumor. Microscopically, benign and malignant forms could be distinguished. The latter were characterized by increased cellularity, prominent mitotic activity, and foci of necrosis or hemorrhage. Follow-up information was obtained in 93 cases. Seventy-one of the 93 patients were living (two with recurrence and four with metastasis), and 22 had died (13 as the result of recurrence or metastasis in more than two-thirds of the related causes). Recurrence preceded metastasis in more than two-thirds of the patients with evidence of metastasis. The 10 year survival rate was 70 per cent. The morphologic differences from other mesenchymal tumors showing a hemangiopericytoma-like vascular pattern are discussed, and the close resemblance of hemangiopericytoma to richly vascular forms of fibrous histiocytomas and synovial sarcoma is emphasized. Congenital or infantile hemangiopericytoma is described as a separate entity having a distinctive microscopic pattern and behavior.

Adolescent↗
PubMed1975

Nuclear division in the ameboflagellate Adelphamoeba galeacystis.

Nuclear division is synchronized cultures of the ameoboflagellate Adelphamoeba galecystis has been described. Division in this organism is typically promitotic. It occurs within an intact nuclear membrane and is characterized by the persistence of the nucleolus and its transformation into 2 polar masses. The nucleolus is stained with pyronin-Y by the methyl green pyronin-Y technic, and with Heidenhain's hematoxylin, but is unstained by the Feulgen reaction. The reaction with these stsins is removed after digestion of the nucleolus by ribonuclease. During mitosis the nucleolus undergoes an orderly series of vacuolizations before forming the polar masses. The chromatin is Feulgen positive, stains with methyl green by the methyl green pyronin-Y technic and undergoes a series of characteristic changes during the division process. Synchronizationof amebae grown on coverglasses was accomplished by transfer of cells from 30 to 38.5 C for a period of 100 min. A temporal sequence of nucleolar and chromatin participation in the nuclear division of this organism is suggested.

Amoeba↗
PubMed1975

Early onset myotonic dystrophy in association with polyneuropathy.

A patient with early onset of myotonic dystrophy, with associated neuropathy and epilepsy, is presented. It is postulated that his disorder was inherited through a recessive, pleomorphic gene. His differential diagnosis is discussed and the literature reviewed. The clinical variability of myotonic dystrophy is stressed and the diagnostic difficulties encountered in the younger age group.

Adolescent↗