Changes in cytosolic calcium, bleb formation, and cell death in neural crest cells treated with isotretinoin and 4-oxo-isotretinoin

Information regarding the cytopathologic mechanism of action of the retinoids [isotretinoin (IR) and 4-oxo-isotretinoin (4-OIR)] on neural crest cells (NCCs) in culture was sought. Those pathophysiologic alterations in cell metabolism studied were: cell blebbing (xieosis), free radical formation, cell viability, and cellular calcium homeostasis. Cells were treated with IR or 4-OIR in the presence of high (1.4 mM) and low (5.0 microM) levels of extracellular calcium ions. Recently developed techniques utilizing fluorescent molecular probes for calcium analyses, i.e., Fura 2AM, were used to study the effects of these drugs on the cytosolic calcium concentration of NCCs. The effects of IR and 4-OIR on NCC viability, [Ca++]int, were contrasted with the effects of certain sulfhydryl drugs (HgCl2, NEM, PCMBS) and calcium ionophores (ionomycin, A23187), agents known to perturb cell membranes, increase cytosolic calcium loads, and induce cell injury and subsequent cell death. Both retinoids were shown to induce an increase in the generation of superoxide radicals (SO) and increase the influx of calcium ions by the NCCs, thus increasing [Ca++]int by several hundred percent within 5 to 10 min. The liberation of SO was calcium dependent. These early effects were accompanied by an increase in cell blebbing activity. Also, a significant decrease in NCC viability was seen as early as 10 min after the addition of IR or 4-OIR to the incubation medium. 4-OIR proved to be the more potent of the two retinoids tested. The severity of these effects on NCC metabolism was dependent on medium calcium concentration with all changes being increased in the presence of the higher extracellular calcium levels. From the data presented it appears as though the retinoids cause a rapid elevation in cytosolic [Ca++]int possibly by purturbing the integrity of the cell membrane, denaturing membrane Ca-ATPase activity, or both. Retinoid-induced changes in membrane activity are evidenced by increased surface blebbing and superoxide formation. The prolonged elevation of intracellular [Ca++] may be directly related to depressed NCC viability and thus explain the known teratogenic effects of these drugs and their relationship to ectomesenchymal cell hypoplasia and craniofacial dysmorphogenesis.

Cryofixation, ultracryomicrotomy, and X-ray microanalysis of enterocytes from chick duodenum: vitamin-D-induced formation of an apical tubulovesicular system

New methods of tissue preparation were developed to study the morphology and distribution of calcium ions in duodenal enterocytes from normal, rachitic, and vitamin D-replete (either cholecalciferol [CC] or 1,25-dihydroxycholecalciferol [1,25-DHCC] treated) chicks. Frozen hydrated sections were prepared from cryofixed tissues by ultracryomicrotomy at -125 degrees C. Sections were subsequently freeze-dried by increasing the temperature to -100 degrees C. The latter temperature was maintained throughout both the structural and elemental analyses. In cells from normal, rachitic, and vitamin D-treated [CC] animals the brush border from lanthanum-infused tissues was electron dense and calcium-lanthanum positive by x-ray analysis. In the absence of lanthanum, i.e., sucrose-infused duodena, the microvilli were still calcium positive. In the terminal web region of normal and CC-treated enterocytes, numerous, apparently interconnected, tubules and vesicles were seen. Vacuole-like structures were also seen. Such structures were especially prominent in the enterocytes from the vitamin-treated [CC] animals. Except for the vacuoles, the tubules and vesicles were electron dense in the lanthanum-infused duodena, and clear in sucrose-infused tissues. In both instances, the structures were calcium positive. Similar, but even larger structures were seen below the terminal web. Here however, the tubules and vesicles seemed to be organized into multiple complex interconnecting networks, i.e., tubulo-vesicular complexes. Both the tubules and the vesicles seemed to be interconnected via smaller channel-like entities. The extensiveness of this structure was better appreciated in the enterocytes from lanthanum-infused tissues, where it appeared similar in structure and complexity to an en face view of the sarcoplasmic reticulum of skeletal muscle. These intestinal complexes were less well developed, decreased in number, and quite often absent, in the apical cytoplasm of absorptive cells from rachitic chicks. In the enterocytes from animals treated for 24 hours with 1,25-DHCC, the same highly developed tubulo-vesicular networks were again seen in the enterocyte apical cytoplasm. They were even more developed in the 1,25-DHCC-treated animals. All structures were intensely calcium positive in enterocytes from both the lanthanum- and the sucrose-infused preparations. Numerous endocytotic (pinocytotic) vesicles were seen at the lumenal plasmalemma. Similar structures were also apparent in the terminal web region of the 1,25-DHCC-treated enterocytes. Exocytotic vesicles were seen at the apical aspect of the lateral cell membrane, below the level of the junctional complex. All components of this unique system contained high concentrations of calcium.(ABSTRACT TRUNCATED AT 400 WORDS)

Duration of liquid water habitats on early Mars

We have employed a simple climate model of early Mars in order to estimate the duration of ice-covered lakes after the onset of freezing conditions on Mars. The critical parameter determining the existence of ice-covered lakes is the existence of peak seasonal temperatures above freezing. The peak temperature occurs at the subsolar point at perihelion. We use the weathering model of Pollack et al. (Icarus 71, 203-224, 1987) to compute the pressure and temperature evolution of the atmosphere. We have included the variability of the solar luminosity. We find that if there was a source of ice to provide meltwater, liquid water habitats could have been maintained under relatively thin ice covers for up to 700 million years after mean global temperatures fell below the freezing point. At this point, the mean annual temperature is 227 K, and the pressure of atmospheric CO2 is about 0.5 bar. Without the presence of stable bodies of liquid water, it is not clear what mechanisms were responsible for the removal of this remaining CO2. From a biological point of view, we find that the duration of liquid water habitats on early Mars exceeds the upper limit on the time required for the origin of life on Mars.

Family planning services: a history of U.S. federal legislation

U.S. Federal legislation related to family planning services for women has been an ongoing process for several decades. Over the years numerous researchers have written about and speculated on many different Congressional acts germane to family planning. Most of these studies, however, have limited their discussions to a specific piece of legislation, its implications, and/or social consequences. The purpose of this study is to present a comprehensive (but relatively brief) history of federal legislation related to family planning services for women of all ages. The list of bills and acts is long and dates back to 1935.

The hospital of the future--planning for change

This paper describes the hospital planning model developed by the North Eastern Metropolitan Region of the Health Department Victoria to forecast acute public hospital bed-day requirements in the Region. Three age-specific variables: population; separation rate; and length of stay have been used to estimate the level of demand for hospital services. The model also delineates services delivered on a same day or long stay basis. The application of the model to three local government areas demonstrates the importance of population growth and ageing on the type and level of hospital services required and the implications thereof for service delivery and the physical configuration of hospitals.

Immunohistochemical and pharmacokinetic characterization of the site-specific immunoconjugate CYT-356 derived from antiprostate monoclonal antibody 7E11-C5

In this study, a site-specific immunoconjugate, designated CYT-356, of the prostate-reactive monoclonal antibody 7E11-C5 was characterized by immunohistological methods for reactivity with normal and neoplastic human tissues. In addition, CYT-356 labeled with 111In was assessed by in vivo imaging and pharmacokinetic studies for localization to human tumor xenografts in nude mice. The native antibody and the site-specific immunoconjugate exhibited similar patterns of reactivity with normal human tissues. Although the majority of tissues tested were negative, weak reactivity with cardiac muscle, proximal kidney tubules, and sweat glands was observed. Positive staining of normal prostate epithelial cells and glandular lumina and strong reactivity with a subset of skeletal muscle cells were also observed. CYT-356 reacted with 100% of prostate tumors examined but was negative on a variety of other neoplasms. Following i.v. administration, CYT-356-111In rapidly localized to and imaged LNCaP human prostate adenocarcinoma xenografts in nude mice, reaching maximal levels of about 30% of injected dose/g of tumor within 3 days. No unusual localization was seen to any nontumor tissue or organ; the level of radioactivity in the normal tissues and organs was at or below that seen in the blood. The localization to xenografts was antigen specific and the accessible binding sites in 100-200-mg tumors appeared to be saturated at an antibody dose between 10 and 100 micrograms. These findings suggest that the CYT-356 immunoconjugate may be useful in the diagnosis and therapy of prostate cancer.

Identification of glyoxylate cycle enzymes in chick liver--the effect of vitamin D3: cytochemistry and biochemistry

Information regarding the presence of the glyoxylate cycle in chick liver was sought. This metabolic pathway has long been thought to be absent from vertebrate tissues. Previous studies in other tissues have shown that, when present, this pathway is sensitive to vitamin-D. Thus, the effect of long-term vitamin-D deficiency and subsequent vitamin-D replacement on liver structure was studied by light microscopy. In addition, specific biochemical assays for the presence of glyoxylate cycle enzymes were performed. Light microscopy of lipid extracted tissues, light microscopic histochemistry, and quantitative histochemistry showed that the hepatocytes from vitamin-D-deficient animals contained primarily lipid. Hepatocytes from normal and vitamin-D-replete livers contained primarily carbohydrate as judged by their staining with periodic acid-Schiff (PAS). Also, malate synthase positive peroxisomes were seen in hepatocytes from normal and vitamin-D-treated chicks. Structures positive for this glyoxylate cycle enzyme were rarely seen in the hepatocytes from vitamin-D-deficient animals. Biochemical analyses showed the presence of the two unique glyoxylate cycle enzymes, isocitrate lyase and malate synthase, in chick hepatocytes. The activity of these enzymes was markedly increased in the vitamin-D-replete livers. In addition, chick hepatocytes demonstrated the capacity to oxidize fatty acid in the presence of cyanide. This activity, which is characteristic of peroxisomal B-oxidation rather than mitochondrial, was stimulated by vitamin-D treatment. Lastly, incubation of chick liver in the presence of a fatty acid substrate (palmitate) led to higher tissue glycogen content. The latter was further increased in liver from vitamin-D-replete animals. These data show the presence of glyoxylate cycle enzymes in a higher vertebrate and indicate that this tissue is endowed with the capacity to convert lipid to carbohydrate.

Immunolocalization of secretory protein-I or chromogranin A in amphibian urinary bladder granular cell granules

The presence of secretory protein-I (SP-I) or chromogranin A (CGA) in granules isolated from the granular cells of the amphibian urinary bladder epithelium was investigated using ultraimmunohistochemistry. Granules were isolated by cell fractionation using Percoll density gradients. SP-I was isolated and purified from bovine parathyroid glands. Antibodies were raised in rabbits and purified by affinity chromatography. Ultraimmunocytochemistry, employing the avidin-biotin-peroxidase (ABC-complex) procedure, was used to localize SP-I on thin sections of isolated granules. About 27% of the granules from control (-ADH) cells were SP-I+, while 51% of the granules fractionated from hormone treated (+ADH) cells were positive for this protein (p less than 0.0001). Accordingly, granules from ADH-treated cells also showed a significant (p less than 0.0001) increase in total protein.

Hibernation activates glyoxylate cycle and gluconeogenesis in black bear brown adipose tissue

Biochemical studies on brown adipose tissue removed from a hibernating black bear and a non-hibernating control animal demonstrate that this tissue: (1) can carry out cyanide-insensitive fatty acid oxidation, and (2) possesses catalase activity and the enzyme activities unique to the glyoxylate cycle, isocitrate lyase and malate synthase. These activities are all markedly increased in brown fat obtained from the hibernating animal. Additionally, hibernation enhances the ability of the tissue to synthesize glycogen in the presence of a fatty acid substrate. The glyoxylate cycle enzymes and the ability to convert fatty acid carbons to glucose have been generally regarded as being absent from vertebrate cells and tissues.

Carbohydrate-derivatized immunoconjugate of the anti-(carcinoembryonic antigen) monoclonal antibody C46: immunohistological reactivity and pharmacokinetic comparison with a randomly derivatized C46 immunoconjugate

In this study, a site-specific glycyl-tyrosyl-(N-epsilon-diethylenetriaminepentaacetic acid)-lysine (GYK-DTPA) immunoconjugate of the anti-carcinoembryonic antigen monoclonal antibody C46 (C46-GYK-DTPA) was characterized by immunohistological and immunofluorescence methods for reactivity with normal and neoplastic human tissues. In addition, pharmacokinetic studies assessed the ability of C46-GYK-DTPA labeled with 111In to localize to and image human tumor xenografts in nude mice. The native antibody and the site-specific immunoconjugate exhibited similar patterns of reactivity with normal human tissues. C46 did not bind to the surface of normal human granulocytes, which indicates lack of reactivity with normal cross-reacting antigen. C46-GYK-DTPA reacted with 100% of the colon, breast and renal carcinomas examined and with two of three lung carcinomas, but did not react with any sarcomas, melanomas or lymphomas examined. Intravenously administered C46-GYK-DTPA-111In rapidly localized to and imaged LS174T human colon adenocarcinoma xenografts in nude mice, reaching maximal levels of about 25% of injected dose/g tumor within 1 day. No unusual localization to any non-tumor tissue or organ was seen; the level of radioactivity in the normal tissues and organs was at or below that in the blood. The accessible binding sites in 1 g tumors appeared to be saturated at an antibody dose between 100 micrograms and 1000 micrograms/mouse. Further, in a direct in vivo comparison, the site-specific conjugate C46-GYK-DTPA had more favorable pharmacokinetics and better tumor localization than a randomly derivatized C46 immunoconjugate (C46-DTPA). These findings suggest that the site-specific immunoconjugate C46-GYK-DTPA may be useful in the diagnosis and therapy of colon cancer and other adenocarcinomas expressing carcinoembryonic antigen.

Retropharyngeal space: evaluation of normal anatomy and diseases with CT and MR imaging

A retrospective analysis of computed tomographic (CT) and magnetic resonance (MR) images and clinical records of 39 patients with retropharyngeal space (RPS) lesions was completed. The review was undertaken to answer the following questions: (a) what is the spectrum of lesions of the RPS? (b) what imaging features mark a lesion as originating in the RPS? and (c) is there a difference between the radiologic pattern of the suprahyoid and infrahyoid portions of the neck? Of the 39 patients in the study, nine had RPS infections, 17 had RPS malignancies, two had benign tumors, seven had RPS pseudotumors, and four had hematoma or air in the RPS after trauma. RPS lesions demonstrated two distinct radiologic patterns: a nodal pattern and a nonnodal pattern. The nodal pattern, found only in the suprahyoid neck, occurs when infection or tumor begins in the lymph nodes of the RPS. The lesions may be unilateral or bilateral, but the middle part of the RPS is spared. The nonnodal pattern, found primarily in the infrahyoid RPS, results when the infection or tumor directly invades the RPS or goes beyond the nodes of the RPS. The nonnodal lesion appears rectangular and spans the RPS from side to side.

Insect hemolymph factor promotes muscle histolysis in Solenopsis

Hemolymph was collected from both normal (virgin) females (control hemolymph) and artificially inseminated females (experimental hemolymph) of Solenopsis, ssp., the imported fire ant (primarily S. invicta and S. geminata). When the control hemolymph was injected into normal females, breakdown of the thoracic flight musculature was not seen 24 hr postinjection. In contrast, when the experimental hemolymph was injected into normal females, flight muscle histolysis was marked 24 hr postinjection. When the experimental hemolymph was heated to 70 degrees C prior to injection into normal females, subsequent flight muscle breakdown was not seen. The injection of freshly collected semen into normal females produced no effect on flight muscle structure. Also, the injection of the experimental hemolymph into normal, alate males produced no muscle histolysis. These observations suggest that the hemolymph from inseminated females contains a factor (or factors) that induces the specific breakdown and subsequent dissolution of the complex thoracic flight musculature. Other thoracic muscles (leg muscles, intersegmental muscles, etc.) are not affected. Based on observations made in both insect muscles as well as vertebrate skeletal muscles, it is suggested that such a hemolymph factor may act by disrupting the structural integrity of muscle cell membranes, resulting in significant changes in membrane permeability, especially with regard to calcium ions.

The immunohistochemical localization of superoxide dismutase activity in the avian epithelial growth plate

Superoxide dismutase (SOD) is a 'scavenger' enzyme which catalyses the dismutation (reduction-oxidation) of the superoxide anion (O2-.), a toxic free radical generated during normal cellular respiration. Light microscopy employing immunohistochemistry was utilized for localizing SOD activity in the chick epiphyseal cartilage. Antibodies to mammalian liver CuZn-SOD were prepared and the avidin-biotin-peroxidase technique (ABC complex) was utilized to localize activity for this enzyme in the growth plate cartilage. The localization of enzyme activity varied in accordance with the characteristic zonation pattern of the growth plate (zone of proliferation, zone of maturation, zone of cell hypertrophy and zone of matrix calcification). In the upper regions of the epiphyseal cartilage (the zones of proliferation and maturation), where the vascularity is poor and the oxygen tension low, SOD activity was localized within the chondrocytes. No extracellular activity was observed. However, in the lower regions of the growth plate (the zones of cell hypertrophy and matrix calcification), where both the vascularity and the oxygen tensions are increased, SOD activity was intense in both the chondrocytes and the surrounding extracellular matrix. Thus, the distribution of SOD enzyme activity in this tissue seems to vary in accordance with the level of oxygen present. The significance of the extracellular SOD activity, seen in the lower aspects of the growth plate cartilage, may indicate the sensitivity of matrix components, especially collagen, to toxic free radicals such as the superoxide anion.

Glyoxylate cycle in the epiphyseal growth plate: isocitrate lyase and malate synthase identified in mammalian cartilage

Peroxisomes were identified in chondrocytes from all zones of the mammalian epiphyseal growth plate by using light microscopic techniques for the cytochemical demonstration of catalase, the marker enzyme for these organelles. Additional cytochemistry showed the presence of malate-synthase-positive structures within the chondrocytes. The latter enzyme, also associated with peroxisomes, is unique to the glyoxylate shunt, a metabolic pathway thought to be absent in vertebrate tissues. The glyoxylate cycle allows the net conversion of lipid to carbohydrate, i.e., gluconeogenesis. Biochemical studies on growth plate cartilage indicate that this tissue has the capacity to carry out cyanide-insensitive B-oxidation of fatty acids. The latter takes place in a nonmitochondrial compartment, most likely the peroxisomal compartment. Additionally, both of the unique enzymes associated with the glyoxylate cycle, i.e., isocitrate lyase and malate synthase, were also identified in a cell-free homogenate of this cartilage. These studies indicate that cartilage, a poorly vascularized tissue characterized by its low oxygen tension and anaerobic glycolysis, may have the capacity to convert lipid to carbohydrate, i.e., gluconeogenesis via the glyoxylate pathway. In this way, cartilage may be unique among mammalian tissues.

The immunocytochemical localization of superoxide dismutase in the enterocytes of the avian intestine: the effect of vitamin D3

Both light microscopical and electron microscopical immunocytochemical techniques were utilized to localize CuZn-superoxide dismutase (SOD) in the duodenum of normal, rachitic and vitamin-D3-replete chicks. This enzyme catalyses the dismutation of the superoxide anion, a toxic free radical generated during the normal aerobic metabolism of most respiring cells. Light microscopy showed no SOD activity associated with the duodenal enterocytes of normal and rachitic chicks. However, in rachitic animals subsequently treated with vitamin D, i.e. vitamin-D-replete chicks, intense immunoreactivity for the enzyme was seen in association with the apical border of the duodenal absorptive cells. Immunostaining for SOD was not seen in goblet cells. With electron microscopy, immunostaining for SOD activity was identified in association with the apical microvilli and, to a lesser degree, with the terminal web, a well as in association with both lysosomes and peroxisomes. From this report it appears that there is a physiological relationship between vitamin D, SOD and the intestinal absorptive cell. However, the precise relationship must await further clarification.

The ultrastructural immunocytochemical localization of superoxide dismutase in the amphibian urinary bladder: effect of aldosterone

Transmission electron microscopy and immunohistochemistry, the latter employing the avidin-biotin-peroxidase (ABC complex) technique, were utilized to localize copper-zinc superoxide dismutase (CuZn-SOD) enzyme activity in the epithelial cells of the toad urinary bladder mucosa. This 'scavenger' enzyme catalyses the dismutation (reduction-oxidation) of the superoxide anion (O2-), a toxic free radical generated during normal cellular respiration. In unstimulated epithelial cells, enzyme activity was seen in the cytosol of granular, mitochondrial-rich and goblet cells. The basal cells were generally devoid of enzyme activity. In addition to the cytosol, SOD activity was also seen in association with the apical plasma membrane of the epithelial cells. In the presence of the steroid hormone aldosterone (10(-7)M, 30 min-6h), CuZn-SOD activity was markedly increased along the luminal mucosal membrane of granular, mitochondrial-rich and goblet cells. This increase was seen as early as 30 min after the addition of hormone, and as long as 6h after treatment. The cytosolic reaction was usually decreased or absent under these conditions. From the data presented, it appears that CuZn-SOD is involved in electrolyte (sodium) transport in the epithelial cells of the toad urinary bladder. The latter may involve hormone-induced alterations in luminal cell membrane structure and chemistry.

Glyoxylate cycle in the rat liver: effect of vitamin D3 treatment

Evidence for the glyoxylate cycle in the mammalian rat liver was sought. Activity of two unique glyoxylate cycle enzymes, isocitrate lyase and malate synthase, was found in rat liver homogenates. Vitamin D3 treatment of rachitic animals produced a five- and fourfold increase, respectively, in the activity of these enzymes. Vitamin D3 also increased the peroxisomal fatty acid oxidation and the accumulation of glycogen in liver slices in the presence of palmitate. These data suggest that the mammalian rat liver can convert fatty acid carbon to carbohydrate carbon directly.

Planetary protection issues in advance of human exploration of Mars

Current planetary quarantine considerations focus on robotic missions and attempt a policy of no biological contamination. The presence of humans on Mars, however, will inevitably result in biological contamination and physical alteration of the local environment. The focus of planetary quarantine must therefore shift toward defining and minimizing the inevitable contamination associated with humans. This will involve first determining those areas that will be affected by the presence of a human base, then verifying that these environments do not harbor indigenous life nor provide sites for Earth bacteria to grow. Precursor missions can provide salient information that can make more efficient the planning and design of human exploration missions. In particular, a robotic sample return mission can help to eliminate the concern about returning samples with humans or the return of humans themselves from a planetary quarantine perspective. Without a robotic return the cost of quarantine that would have to be added to a human mission may well exceed the cost of a robotic return mission. Even if the preponderance of scientific evidence argues against the presence of indigenous life, it must be considered as part of any serious planetary quarantine analysis for missions to Mars. If there is life on Mars, the question of human exploration assumes an ethical dimension.

The glyoxylate cycle in rat epiphyseal cartilage: the effect of vitamin-D3 on the activity of the enzymes isocitrate lyase and malate synthase

The effect of vitamin-D deficiency and subsequent vitamin-D replacement on the metabolism of rat epiphyseal growth plate cartilage was studied. Biochemical analyses showed the presence of the two unique glyoxylate cycle enzymes isocitrate lyase and malate synthase in cartilage. The activity of these enzymes was markedly increased after treatment with the vitamin. Additionally, rat cartilage showed the capacity to oxidize fatty acid in the presence of cyanide. This cyanide-insensitive fatty acid oxidation is characteristic of peroxisomal B-oxidation rather than mitochondrial B-oxidation. Vitamin-D treatment also increased fatty acid oxidation. Lastly, incubation of rat cartilage in the presence of a fatty acid substrate such as palmitate, resulted in a higher tissue glycogen content. Tissue glycogen was further elevated by vitamin-D. Such data indicate the presence of glyoxylate cycle enzymes in a vertebrate tissue and raise the possibility that mammalian cartilage has the capacity to convert lipid to carbohydrate.

Effects of contrast media on calcium transients and motion in cultured ventricular cells

To investigate the mechanisms of the negative inotropic effects of contrast media, we superfused spontaneously contracting cultured chick embryo ventricular cells with Renografin-76 and iohexol (12% solutions), and hypertonic sucrose during simultaneous measurement of [Ca2+]i transients (indo-1) and motion (video-motion detector system). Exposure to contrast agents caused a significant reduction of contractility, with Renografin-76 having a much greater effect on amplitude of motion than iohexol. Renografin-76 significantly depressed [Ca2+]i transient amplitude, whereas iohexol had no effect. Addition of Ca2+ to correct for calcium binding by Renografin-76 completely reversed its depression of [Ca2+]i transients but only partially reversed the negative inotropic effects. Hypertonic sucrose caused a significant decrease in contraction amplitude, with no significant effects on [Ca2+]i transient amplitude. We conclude that the marked negative inotropic effect of Renografin-76 is caused by both calcium binding and hypertonicity. The less marked depression of contractility produced by iohexol likely is a result of hypertonicity and not caused by alteration of [Ca2+]i.

Electron microscopic cytochemical localization of Ca-ATPase in the rod outer segments of the toad Bufo marinus

Transmission electron microscopy and ultracytochemistry were employed in an attempt to localize the enzyme calcium adenosine triphosphatase (Ca-ATPase) in the rod outer segments (ROS) of the toad retina. Utilizing a one-step incubation procedure, Ca-ATPase was identified as an electron-dense precipitate in the intradiskal spaces of the rod disks (vesicles) of the ROS. Analytical microscopy identified the reaction product as lead phosphate. The formation of the reaction product was dependent on the presence of ATP (the substrate) and calcium ions. However, calcium ions could be substituted for by magnesium ions. In addition, the reaction was vanadate sensitive. The latter is known to inhibit Ca-ATPase activity. Such data appear to indicate the presence of a Ca-Mg-ATPase in association with the rod disks. Since cyclic guanosine monophosphate (cyclic GMP), rather than calcium ions, is currently believed to be the primary intracellular messenger associated with phototransduction, the presence of an ROS Ca-ATPase may indicate other functions for this cation in the physiology and biochemistry of the visual process. Ca-ATPase might play a role in directional calcium fluxes between intracellular compartments.

Quantitation of phagocytic cells in phenytoin-induced connective tissue proliferation in the rat

This study demonstrates that, in rats, systemically administered phenytoin produces a statistically significant increase in accumulation of phagocytic and esterase positive cells in areas of phenytoin-induced connective tissue proliferation. Many of these cells are perceived to be macrophages. Since macrophages have been shown to produce chemoattractant and mitogens for fibroblasts, they may very well play a major role in the gingival hyperplasia seen in patients taking phenytoin. The results of the study show that the effects of phenytoin on fibroblasts may be more complex than previously thought.

Electron microscopic cytochemical localization of a basolateral calcium adenosine triphosphatase in vitamin D replete chick enterocytes

A cytochemical technique for the electron microscopic localization of calcium adenosine triphosphatase (Ca-ATPase) was utilized to localize this enzyme in the enterocytes of rachitic and vitamin D-replete chicks. In animals treated with cholecalciferol (CC, vitamin D3), an electron-dense reaction product was located along the basolateral membranes of the absorptive cells within 72 hr after injection. Similarly, a reaction product was identified in association with the basolateral membranes within 24 hr after injection of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D. A microvillar reaction product was not seen in either of these two groups. Electron-dense reaction products were also seen in association with mitochondria and scattered throughout the cytoplasm of these enterocytes. The Ca-ATPase reaction product was dependent upon the presence of medium calcium and substrate (ATP), was inhibited by vanadate, and was heat labile. In the rachitic animals, a reaction product indicative of Ca-ATPase activity was not seen in association with either the basolateral membranes or the mitochondria. These data appear to indicate that an energy-requiring calcium-activated membrane pump plays a role in the flux of calcium across the enterocytes of the small intestine.