Projection status of calbindin- and parvalbumin-immunoreactive neurons in the superficial layers of the rat's superior colliculus.

Immunocytochemistry and retrograde labeling were used to define the thalamic projections of calbindin- and parvalbumin-containing cells in superficial layers of the rat's superior colliculus (SC). Quantitative analysis revealed that 90.8 +/- 2.2% (mean +/- standard deviation) of the calbindin-immunoreactive neurons in the stratum griseum superficiale (SGS) projected to the dorsal lateral geniculate nucleus (LGNd) and that 91.3 +/- 4.3% of calbindin-immunoreactive neurons in the stratum opticum (SO) projected to the lateral posterior nucleus (LP). In contrast, only 17.3 +/- 2.5% of parvalbumin-immunoreactive neurons in the SGS were found to project to the LGNd and 16.5 +/- 3.1% of the parvalbumin-immunoreactive SO cells were retrogradely labeled after LP injections. Few of the parvalbumin-immunoreactive neurons in either the SGS (7.2 +/- 2.5%) or the SO (9.2 +/- 2.5%) were GABA positive. The retrograde-labeling results suggest that parvalbumin-immunoreactive neurons in the rat's SO and SGS may either be primarily interneurons or have descending projections, while calbindin-containing cells are primarily thalamic projection neurons. These results are consistent with data from other rodents, but almost exactly the opposite of data that have been reported for the cat for these same populations of SC projection neurons. Such interspecies differences raise questions regarding the functional importance of expressing one calcium-binding protein versus another in a specific neuronal population.

Differential age-dependent effects of retinal deafferentation upon calbindin- and parvalbumin-immunoreactive neurons in the superficial layers of the rat's superior colliculus.

Several recent studies have reported varied effects of different forms of visual deprivation on the expression of calcium-binding proteins in the CNS. Most of these studies have surveyed only a single protein from this family and have not systematically evaluated the influence of the age of the animal upon the effects observed. The present study combined immunocytochemistry and quantitative morphometry to determine the effects of eye removal in fetal life, at birth, or in adulthood upon the expression of calbindin and parvalbumin by neurons in the retinorecipient laminae (the stratum griseum superficiale (SGS) and stratum opticum (SO)) of the rat's superior colliculus (SC). Both fetal and neonatal enucleation significantly reduced the total number of neurons in the SGS. Eye removal at any age did not significantly affect the number of neurons in the SO or the proportion of SGS or SO cells that expressed calbindin. Adult enucleation produced a significant increase in the percentage of SGS cells expressing parvalbumin. These results suggest that calbindin expression is highly stable in visual neurons while parvalbumin expression is more plastic and appears to be suppressed by retinal input.

Immunochemical heterogeneity in the tecto-LP pathway of the rat.

The projection from the rat's superior colliculus (SC) to the lateral posterior nucleus of the thalamus (LP) has previously been described as arising from a morphologically homogeneous population of neurons in the stratum opticum (SO). The present study combined immunocytochemistry with retrograde tracing and lesion techniques to determine whether or not the SC-->LP projection arose from neurons that were also neurochemically homogeneous. The combination of retrograde tracing and immunocytochemistry with an antibody directed against calbindin-D 28K (CBD) showed that 64.4% of the neurons that project from SC to LP contain this calcium-binding protein. Retrograde tracing and immunocytochemistry for adenosine deaminase (ADA) showed that a smaller number of tecto-LP cells (15.7%) were immunoreactive (IR) for this enzyme. Moreover, nearly all (93.0%) of the ADA-IR tecto-LP cells also contained CBD-IR. Adenosine deaminase-IR axons in LP were restricted to the dorsomedial portion of the nucleus and their density was substantially reduced after ablation of the ipsilateral superficial SC laminae. The lateral posterior nucleus contained numerous CBD-IR cells and fibers throughout its extent and it was thus difficult to determine the extent to which the extra-perikaryal CBD-IR in this nucleus was dependent upon the tecto-LP pathway. Nevertheless, destruction of the ipsilateral SC did reduce the density of CBD-IR in LP. These results suggest that the SC-->LP projection in rat arises from at least four neurochemically distinct cell groups: 1) those that contain CBD, 2) those that contain both CBD and ADA, 3) a very small population that contains only ADA, and 4) a group that is not recognized by either of these markers. Our results further suggest that ADA containing fibers may have a more restricted terminal distribution in LP than axons that contain only CBD.

A comparison of the intracellular distribution of mu-calpain, m-calpain, and calpastatin in proliferating human A431 cells.

Little is known about the relative intracellular localizations of the calcium-dependent proteases, calpains, and their naturally occurring inhibitor, calpastatin. In the present study, the intracellular localization of mu-calpain, m-calpain, and calpastatin was studied at the light microscopic level in proliferating A431 cells. Highly specific antibodies against the three antigens revealed distinct staining patterns in interphase and mitotic cells. Most notably, calpastatin in interphase cells was localized near the nucleus in tube-like, or large granular structures, while the calpains were more uniformly distributed through the cytoplasm in either a fibrillar form (mu-calpain) or a diffuse or fine granular form (m-calpain). The distribution patterns of the two calpain isozymes were distinctly different during mitosis. m-Calpain was concentrated at the mitotic spindle poles and midbody, while mu-calpain appeared to accumulate at the cell membrane and the spindles. Four other human cell lines as well as normal human monocytes were examined to determine if the calpains-calpastatin segregation patterns are common to other cells or are unique to the A431 line. With the exception of abundant nuclear mu-calpain in the C-33A cervical carcinoma, the segregation of the proteins was similar to that of A431. These studies indicate that calpains may be localized at regions which are relatively poor in calpastatin content. Proteins at these sites may be susceptible to calpain-catalyzed cleavage.

Communicating intrathoracic hydrocele.

Tense ascites may cause herniation of parietal peritoneal reflection into the mediastinum at the gastroesophageal junction. This may produce a mass visible on chest radiograph and computed tomography (CT). This communicating intrathoracic hydrocele may occur in the absence of hiatal hernia and may be confused with other middle mediastinal fluid collections including necrotic tumor, abscess, cyst of foregut origin, or pancreatic pseudocyst. Recognition of this entity in patients with ascites should prevent diagnostic confusion and unnecessary further evaluation.

Interactive videodisc as an instructional tool in medical education.

At a time when medical educators are actively revising the undergraduate medical school curriculum to make it more responsive to exigencies of the 21st century, the use of interactive videodisc technology may well prove to be a significant addition. Using interactive videodisc technology may be instrumental in reducing the amount of a large lecture didactic learning and improving small group problem-solving sessions that better synthesize factual knowledge. It also provides important and valuable exposure to varieties of computer technology that play an increasingly important role in training and medical practice.

Issues in the adoption of a new educational technology.

The interactive laser videodisc, with its large data base and rapid random access capability, has the potential to play a significant role in health care education. The introduction of this new technology in the last few years has been made difficult by several barriers to the acceptance of the technology. These barriers are grouped into issues of cost, quality and the resistance to change.

Intracranial extravasation of contrast medium during carotid angiography.

The results of 5184 carotid angiograms were reviewed and five cases of intracranial extravasation of contrast medium were found. In two cases an aneurysm ruptured during angiography and extravasation into the subarachnoid space was seen. In one case medium leaked from an angiomatous malformation into the subdural space. The fourth case was a patient who had suffered closed head trauma. Here extravasation was seen deep within the brain. The fifth case illustrates two forms which extravasation from meningeal arteries may take. The incidence and prognostic significance of this finding in different conditions are discussed.