Electron microscopic immunocytochemical evidence that the calmodulin-dependent cyclic nucleotide phosphodiesterase is localized predominantly at postsynaptic sites in the rat brain.

The calmodulin-dependent cyclic nucleotide phosphodiesterase represents an important junction between the Ca2+ and the cyclic AMP/cyclic GMP second messenger systems. In brain it is a major cyclic nucleotide-degrading activity and is selectively expressed in the soma and dendrites of regional output neurons [Kincaid et al. (1987) Proc. natn. Acad. Sci. U.S.A. 84, 1118-1122]. In this study the subcellular localization of this enzyme in cerebral cortex, hippocampus and inferior colliculus of rat brain was analysed by electron microscopic immunocytochemical methods using affinity-purified antibodies. The immunoreactivity was found exclusively within neurons whereas glial cells were unstained; preabsorption of antibody with phosphodiesterase eliminated this reactivity, demonstrating the specificity of immunostaining. In the neuronal cell bodies, deposits of immunoreaction product occurred as sparse patches in the cytoplasm and were often associated with organelles such as mitochondria, Golgi-complex and endoplasmic reticulum; nuclei, however, were free from immunoreaction product. In the neuronal processes immunoreactivity was found within dendrites and dendritic spines, whereas the myelinated axons and axon terminals were immunonegative. The postsynaptic densities of asymmetric synapses were associated with especially high concentrations of immunoreaction product. However, the immunopositive synaptic profiles appeared to be quite selective, comprising only a small percentage of the total number of synapses in the neuropil. Our results indicate that the calmodulin-dependent cyclic nucleotide phosphodiesterase is concentrated at postsynaptic sites in specific classes of neurons. This finding supports other morphological evidence indicating a primary role for cyclic nucleotide action in postsynaptic and not presynaptic structures. Furthermore, since this enzyme is regulated by Ca2+, this interface between second messenger systems seems to play a significant role in the postsynaptic integration of Ca(2+)-mediated neuronal inputs.

Autosomal recessive polycystic kidney disease: characterization of human peritoneal and cystic kidney cells in vitro.

Renal cystic epithelia and peritoneal mesothelia from two humans with autosomal recessive polycystic kidney disease (ARPKD) were grown in culture. Cystic epithelial and mesothelial cells formed continuous monolayers in vitro. By electron microscopy, cystic renal cells exhibited a single apical cilium and numerous short, stubby microvilli, both in situ and in vitro. Mesothelial cells exhibited intra- and extracellular membrane-limited, lipid-filled vesicles and surface microvilli. Cystic kidney cells in vitro stained positive for lectins from Cancanavalia ensiformis (concanavalin A), Triticum vulgaris, Erythrina cristagalli, Ulex europeaus, and Arachis hypogaea. Immunocytochemical and lectin staining revealed the renal and peritoneal cells to be of collecting tubule and mesothelial origin, respectively. Both cell types showed large depositions of glycogen granules in the cytoplasm during propagation in certain culture media; in kidney cells, dibutyryl cyclic adenosine monophosphate (cAMP) abolished glycogen depositions. Glycogen deposition also was observed in liver tissue obtained by needle biopsy from one patient. No bacteria were cultured from nor endotoxin detected in the renal cyst fluid. Relative to serum, the cyst fluids contained low sodium, potassium, and chloride levels. Thus, cultured ARPKD cells demonstrate a number of characteristics that are different from cells derived from the autosomal dominant form of renal cystic disease (ADPKD).

Unilateral demodectic rosacea.

A unilateral rosacea-like chronic dermatitis of the right side of the face was shown to harbor innumerable Demodex folliculorum and D. brevis. Treatment with oral metronidazole suppressed the dermatitis but did not significantly reduce the Demodex population. Treatment with topical crotamiton eliminated the Demodex and was curative. These observations support the view that D. folliculorum and D. brevis may be pathogenic when they are present in extremely large numbers.

Staphylococcus aureus colonization of burrows in erythrodermic Norwegian scabies. A case study of iatrogenic contagion.

Scanning electron microscopy demonstrated extensive bacterial colonization of scabies burrows honeycombing the stratum corneum of an elderly woman with erythroderma. Cultures of scybala revealed hemolytic Staphylococcus aureus, possibly responsible for the erythroderma. Epidemiologic data revealed a trail of scabies through two nursing homes and one hospital during the 2-year period that physicians believed she had a drug-induced erythroderma.

The laminate capillary and its wall of multiple basement membranes.

Cutaneous telangiectatic vessels from two cases of unilateral dermatomal superficial telangiectasia were shown under electron microscopy to be venular capillaries with thick walls composed of multiple basement membranes. We suggest that this special capillary structure, seen in a variety of telangiectatic and disease states, should be called the 'laminate capillary'.

Naproxen-induced pseudoporphyria presenting a diagnostic dilemma.

A case of clinical porphyria cutanea tarda posed a diagnostic dilemma when screening tests for porphyrinuria gave negative results and two skin biopsy specimens failed to show the histologic picture of porphyria cutanea tarda, pseudoporphyria, or epidermolysis bullosa acquisita. The dilemma was resolved when the eruption cleared following elimination of naproxen from the patient's treatment. Subsequent naproxen challenge resulted in new bullae on the dorsum of the hands.

The infected hairs of tinea capitis due to Microsporum canis: demonstration of uniqueness of the hair cuticle by scanning electron microscopy.

Scanning and transmission electron microscopic studies were done on scalp hairs of four patients infected with ectothrix Microsporum canis. Both freeze fracture and cross-sectioning of hairs revealed a thick sheath of fungal spores encircling the hair shaft beneath an intact cuticle. These spores were not visible on surface inspection but became apparent only where the cuticle had been rubbed off or broken. Daily selenium sulfide shampoos removed all of the spores from these sites. The cuticle is viewed as being an effective barrier to the penetration of fungi, so that the hair is vulnerable to fungus infection only deep within the hair follicle below the level of the mature cuticle. Once the fungus enters the hair cortex just above the hair bulb, it produces myriads of spores that remain trapped and hidden beneath the cuticle for the length of the intact hair.

Argyria: the intradermal "photograph," a manifestation of passive photosensitivity.

X-ray microprobe and electron microscopic study was made of the remarkable blue-black pigmentation that sunlight elicits in patients with argyria. The patient under study had developed argyria following injection of silver nitrate as a sclerosant into his varicose veins 41 years ago. Similarities are demonstrated between the darkening of the skin and the darkening of a photographic film following light exposure. In both instances, colorless silver salts and compounds present in an inert matrix (collagen versus gelatin) are reduced by incident light to black metallic silver. This passive photosensitivity reaction leads to silver tattooing of the light-exposed skin and to photographic imaging in the film.

Melanosome macrocomplex: an ultrastructural component of patterned and nonpatterned seborrheic keratoses.

An ultrastructural study of five seborrheic keratoses arising in a symmetrical, patterned distribution following the lines of cleavage on the backs of two patients showed the presence of melanosome macrocomplexes 2 to 5 microns in size. Identical findings were seen in fifteen pigmented seborrheic keratoses randomly distributed on the skin of five patients. The membrane-bound macrocomplexes were clusters of closely packed, discrete melanosomes. Present in melanocytes, keratinocytes, Langerhans cells, and dermal macrophages, they were considered to result from sequestration of melanosomes in cell phagosomes. No homogeneous inclusions typical of melanin macroglobules ("giant melanosomes") were found in any of the specimens, supporting the view that neither patterned nor nonpatterned seborrheic keratoses are nevoid in nature.

Demonstration of a unique viral structure: the molluscum viral colony sac.

Using scanning electron microscopy to study molluscum contagiosum lesions, it has been possible to demonstrate a unique, well defined sac enclosing the virion colony of each infected keratinocyte. This confirms the presence of a structure demonstrated over 50 years ago by micro-dissection, but ignored since it is not seen on either light or transmission electron microscopy. It is postulated that this sac, of unknown origin, favours replication of the virions by providing a site that is both anatomically and immunologically privileged. Such relatively unimpeded growth of the virions results in an enlarged cell in which the cytoplasm and nucleus are compressed into a thin outer shell. In the aggregate, this produces a tumour of virus-packed cells rather than a tumour composed of virus-induced cell hyperplasia.