Crystallization and preliminary X-ray analysis of D-2-hydroxyacid dehydrogenase from Haloferax mediterranei

D-2-hydroxyacid dehydrogenase (D2-HDH) from Haloferax mediterranei has been overexpressed in Escherichia coli, solubilized in 8 M urea and refolded by rapid dilution. The protein was purified and crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate or PEG 3350 as precipitant. Two crystal forms representing the free enzyme and the nonproductive ternary complex with alpha-ketohexanoic acid and NAD(+) grew under these conditions. Crystals of form I diffracted to beyond 3.0 A resolution and belonged to the monoclinic space group P2(1), with unit-cell parameters a = 66.0, b = 119.6, c = 86.2 A, beta = 96.3 degrees . Crystals of form II diffracted to beyond 2.0 A resolution and belonged to the triclinic space group P1, with unit-cell parameters a = 66.5, b = 75.2, c = 77.6 A, alpha = 109.1, beta = 107.5, gamma = 95.9 degrees. The calculated values for V(M) and analysis of the self-rotation and self-Patterson functions suggest that the asymmetric unit in both crystal forms contains two dimers related by pseudo-translational symmetry.

Antibiotic activity and characterization of BB-3497, a novel peptide deformylase inhibitor

Peptide deformylase (PDF) is an essential bacterial metalloenzyme which deformylates the N-formylmethionine of newly synthesized polypeptides and as such represents a novel target for antibacterial chemotherapy. To identify novel PDF inhibitors, we screened a metalloenzyme inhibitor library and identified an N-formyl-hydroxylamine derivative, BB-3497, and a related natural hydroxamic acid antibiotic, actinonin, as potent and selective inhibitors of PDF. To elucidate the interactions that contribute to the binding affinity of these inhibitors, we determined the crystal structures of BB-3497 and actinonin bound to Escherichia coli PDF at resolutions of 2.1 and 1.75 A, respectively. In both complexes, the active-site metal atom was pentacoordinated by the side chains of Cys 90, His 132, and His 136 and the two oxygen atoms of N-formyl-hydroxylamine or hydroxamate. BB-3497 had activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis, and activity against some gram-negative bacteria. Time-kill analysis showed that the mode of action of BB-3497 was primarily bacteriostatic. The mechanism of resistance was via mutations within the formyltransferase gene, as previously described for actinonin. While actinonin and its derivatives have not been used clinically because of their poor pharmacokinetic properties, BB-3497 was shown to be orally bioavailable. A single oral dose of BB-3497 given 1 h after intraperitoneal injection of S. aureus Smith or methicillin-resistant S. aureus protected mice from infection with median effective doses of 8 and 14 mg/kg of body weight, respectively. These data validate PDF as a novel target for the design of a new generation of antibacterial agents.

Synaptic organisation of lumbar sympathetic ganglia of guinea pigs: serial section ultrastructural analysis of dye-filled sympathetic final motor neurons

The authors serially sectioned seven dye-filled neuronal somata and more than 1.6 mm of their dendrites from the lumbar sympathetic ganglia of guinea pigs and examined them ultrastructurally to determine the distribution of preganglionic synaptic inputs to their dendrites and cell bodies. Most of the surface of the neurons was covered with Schwann cells. Apposing boutons were rare, with an average density of one axosomatic bouton per 125 microm2 of somatic membrane and one axodendritic bouton per 25 microm of dendrite. Many dendritic segments that were more than 50 microm long completely lacked any apposing boutons. Although the average density of apposing boutons was low, local densities could be high, so that clusters of up to four adjacent boutons occurred on cell bodies and dendrites alike. The spatial arrangement of the apposing boutons for each of the cells examined here was not significantly different from a random distribution. Consequently, the number of apposing boutons observed for any neuron was simply proportional to the amount of neuronal surface sampled in the serial section run. About 50% of boutons directly apposing the neurons lacked any detectable presynaptic specialisations. When they were present, the presynaptic densities had a mean length of about 220 nm, with no difference between boutons that made axosomatic or axodendritic appositions. By applying these data to complete reconstructions of the dendritic trees of dye-filled sympathetic neurons at the light microscopic level, the authors estimated that few neurons in the lumbar sympathetic chain of guinea pigs would receive more than 200 synapses or apposing boutons and that many of them would receive less than 100 synapses. Up to 50% of these boutons would be predicted to make axosomatic contacts. These new observations provide a strong morphological framework for a better understanding of how sympathetic final motor neurons process their preganglionic synaptic inputs.

Distribution of the alpha1 to alpha6 chains of type IV collagen in bovine follicles

During follicular development the proliferative and differentiated state of the epithelioid granulosa cells changes, and the movement of fluid across the follicular basal lamina enables the formation of an antrum. Type IV collagen is an important component of many basal laminae. Each molecule is composed of three alpha chains; however, six different type IV collagen chains have been identified. It is not known which of these chains are present in the follicular basal lamina and whether the type IV collagen composition of the basal lamina changes during follicular development. Therefore, we immunolocalized each of the six chains in bovine ovaries using antibodies directed to the nonconserved non-collagenous (NC) domains. Additionally, dissected follicles were digested with collagenase to release the NC domains, and the NC1 domains were then detected by standard Western immunoblot methods. The follicular basal lamina of almost all primordial and preantral follicles was positive for all type IV collagen alpha chains. Colocalization of type IV collagen and factor VIII-related antigen allowed for discrimination between the follicular and endothelial basal laminae. Type IV collagen alpha1, alpha2, alpha3, alpha4, and alpha5 chains were present within the follicular basal lamina of only a proportion of antral follicles (17 of 22, 20 of 21, 15 of 18, 14 of 28, and 12 of 23, respectively), and staining was less intense than in the preantral follicles. Staining for the alpha1 and alpha2 chains was diffusely distributed throughout the theca in regions not associated with recognized basal laminae. The specificity of this immunostaining for alpha1 and alpha2 chains of type IV collagen was confirmed by Western immunoblots. As well as being detected in the basal lamina of approximately half of the antral follicles examined, type IV collagen alpha4 also colocalized with 3beta-hydroxysteroid dehydrogenase-immunopositive cells in the theca interna. Type IV collagen alpha6 was detected in the basal lamina of only one of the 16 antral follicles examined. Thus, the follicular basal lamina changes in composition during follicular development, with immunostaining levels being reduced for all type IV collagen chains and immunoreactivity for type IV collagen alpha6 being lost as follicle size increases. Additionally, immunoreactivity for alpha1 and alpha2 appears in the extracellular matrix of the theca as it develops.

Synaptic organisation of neuropeptide-containing preganglionic boutons in lumbar sympathetic ganglia of guinea pigs

Within the lumbar sympathetic ganglia of guinea pigs, the endings of different populations of neuropeptide-containing preganglionic neurons form well-defined pericellular baskets of boutons around target neurons in specific functional pathways. We have used multiple-labelling immunofluorescence, confocal microscopy, and ultrastructural immunocytochemistry to investigate synaptic organisation within pericellular baskets labelled for immunoreactivity to calcitonin gene-related peptide (CGRP), substance P (SP), or the pro-enkephalin-derived peptide, met-enkephalin-arg-gly-leu (MERGL) in relation to their target neurons. Different functional populations of neurons, identified by their neurochemical profile, showed a significant degree of spatial clustering and predicted well the distribution of specific classes of pericellular baskets. Most of the boutons in a basket were completely surrounded by Schwann cell processes and did not form synapses. The synapses that were present were made mostly onto dendrites enclosed by the Schwann cell sheath surrounding the neuron within the basket. These dendrites probably originated from neurochemically similar neighbouring neurons. Nevertheless, some of the boutons in the baskets did form synapses with the cell body or proximal dendrites of the neuron they surrounded. Occasionally, cell bodies received a relatively high number of synapses and close appositions from boutons in a pericellular basket. Synaptic convergence of two immunohistochemically distinct types of preganglionic inputs was found in baskets of SP-immunoreactive or MERGL-immunoreactive, but not CGRP-immunoreactive, boutons. Taken together, our results show that the appearance of pericellular baskets is primarily due to the packing of the target neurons. The grouping of functionally similar classes of neurons with their pathway-specific projections of peptide-containing preganglionic neurons suggests that peptides could exert their effects in relatively well-defined zones within the ganglia.

Differential localization of laminin chains in bovine follicles

The composition of a basal lamina markedly affects its ability to filter material and affects the fate of adjacent epithelial cells. Therefore, basal laminae differ in composition with tissue development, and between different tissues in the body. Laminins are a component of basal laminae and consist of one alpha, one beta and one gamma chain, of which there are at least five, three and two isoforms, respectively. This is the first study to immunolocalize a range of these individual laminin chains (alpha 1, alpha 2, beta 1, beta 2, gamma 1) in ovarian follicles. Frozen sections of bovine ovaries (n = 6) were immunostained using specific antisera to laminin chains and factor VIII-related antigen (to identify endothelial cells). Secondary antisera were labelled with one of two different fluorochromes (DTAF and Cy3), and dual localization of laminin chains and factor VIII-related antigen was performed. The alpha 1, beta 2 and gamma 1 chains were consistently localized to the follicular basal lamina in all healthy follicles. Staining was less intense in the atretic antral follicles. Conversely, alpha 2 and beta 1 were rarely present in the follicular basal laminae of healthy antral follicles. Two of nine healthy antral follicles observed stained weakly for alpha 2 in their basal lamina, and beta 1 was present at low concentrations in growing preantral follicles. In atretic antral follicles, the follicular basal lamina stained positively for alpha 1, alpha 2, and beta 2 but no beta 1 was detected and the gamma 1 staining was less intense than in healthy follicles. Antisera to Englebreth Holm-Swarm tumour laminin stained basal laminae of all follicles. In the theca of antral follicles, beta 1 and beta 2 chains were both present in the vasculature. Staining for the gamma 1 chain was present in the thecal vasculature and generally throughout the theca of healthy and atretic antral follicles. Therefore, the composition of the follicular basal lamina alters during development and atresia, and potentially plays a role in the changing identity of the granulosa cells and the accumulation of antral follicular fluid.

Crystallization of cytochrome b562 from Erwinia chrysanthemi

Cytochrome b(562) from Erwinia chrysanthemi has been crystallized using the hanging-drop vapour-diffusion method with ammonium sulfate as the precipitant. X-ray precession photographs show that the crystals formed belong to either of the enantiomorphic space groups P4(1)2(1)2 or P4(3)2(1)2 with the cell parameters a = b = 98.6 and c = 62.7 A. Estimation of the crystal density and consideration of the possible values for V(m) indicate that there is either a dimer or trimer in the asymmetric unit. Experiments using the synchrotron radiation source at the CCLRC Daresbury Laboratory have shown that the crystals diffract to at least 2.7 A resolution. An analysis of the N-terminal sequence indicates that this cytochrome shows limited homology to the cytochrome b(562) from E. coli. Determination of the structure will therefore allow analysis of the relationship between these two proteins.

Production of extracellular matrix, fibronectin and steroidogenic enzymes, and growth of bovine granulosa cells in anchorage-independent culture

A proportion of the granulosa cells from bovine antral follicles will survive, like stem cells, in anchorage-independent culture. To study these cells, bovine granulosa cells were isolated from medium-sized follicles (3-5 mm), plated out (in aliquots of 2.5 x 10(4) viable cells) onto a 1 mL agar base, and overlaid with 1 mL of methycellulose solution in culture medium (control). The cells were cultured (14 days) and then processed for histology (n = 14) or Western immunoblotting (n = 5). Under control conditions or after treatment with basic fibroblast growth factor (bFGF; 50 ng mL-1), a proportion of the granulosa cells divided to produce colonies; individual cells remained small. bFGF increased the number of cells harvested (15.8 +/- 7.3-fold, as measured indirectly by the relative amount of the nuclear La antigen), increased the average diameter of the colonies from 88.9 +/- 13.5 microns to 136.5 +/- 4.9 microns and stimulated the production of fibronectin 5.7 +/- 1.5-fold (P < 0.05). An extracellular matrix, which has previously been shown to be a basal lamina, was observed in 19.1% of the colonies (total of 350 colonies examined; n = 8 experiments). Cells treated with dibutyryl cAMP (1 mM) hypertrophied and had 50 +/- 28.7-fold and 102.6 +/- 55.8-fold higher levels of cholesterol side-chain cleavage cytochrome P450 (P < 0.001) and 3 beta-hydroxysteroid dehydrogenase (P < 0.01) respectively (n = 5). Thus, granulosa cells with characteristics of stem cells can divide and produce extracellular matrix, or be induced to differentiate when in culture without anchorage.

Basal lamina and other extracellular matrix produced by bovine granulosa cells in anchorage-independent culture

Bovine granulosa cells from 3-7 mm follicles were cultured without anchorage in soft agar/methylcellulose solution for 14 days, with or without 50 ng/ml basic fibroblast growth factor. The granulosa cells divided to form colonies of cells. These were analysed by light and electron microscopy, immunohistochemistry and Western immunoblotting. In approximately 20% of the colonies extracellular matrix was clearly visible at the light-microscope level. Ultrastructurally the matrix resembled a basal lamina 30-100 nm thick and was composed of tangled fibres or cords. Unidentified spherical structures of less than 50 nm diameter were sometimes present and attached to this basal lamina. The basal lamina of follicles had similar features, except that the basal lamina produced in vitro was a large aggregate of many convoluted layers. The cells produced collagen type IV and the cellular form of fibronectin. Intercellular areas not associated with basal lamina were identified. Ruthenium red staining revealed these areas to be rich in proteoglycan granules. Free granules were clustered near the cell surface, and the lumina of these areas were rich in fibres decorated with ruthenium red. This material did not resemble follicular fluid of antral follicles. Thus, granulosa cells in anchorage-independent cultures have a follicular cell morphology and secrete two distinct extracellular matrices, one similar to the follicular basal lamina.

Crystallization and analysis of the subunit assembly and quaternary structure of imidazoleglycerol phosphate dehydratase fromSaccharomyces cerevisiae

Imidazoleglycerol phosphate dehydratase (IGPD) from Saccharomyces cerevisiae has been crystallized in the presence of a range of divalent cations using the hanging-drop method of vapour diffusion with ammonium sulfate or polyethylene glycol (PEG) 4000 as the precipitants. X-ray precession photographs have established that the crystals formed with ammonium sulfate (form A) belong to the space group F432, with cell parameter a = 177.5 A and a single subunit in the asymmetric unit. A preliminary data set collected to 6 A resolution on a two-detector San Diego Multiwire area detector has established that the crystals formed with PEG 4000 (form B) belong to either of the special pair of space groups I23 or I2(1)3, with cell parameter a = 131.0 A. A self-rotation function has been calculated using these data and indicates that the cell axes show pseudo fourfold symmetry consistent with a dimer in the asymmetric unit in this crystal form. Light-scattering studies indicate that in the presence of Mn(2+) and a number of other divalent cations IGPD undergoes assembly to a particle of molecular weight approximately 500 kDa. Given the subunit molecular weight of 23 kDa together with the symmetry of the crystals it would indicate that the most likely quaternary structure for this enzyme is based on a 24-mer in 432 symmetry.

The physiology of the ovary: maturation of ovarian granulosa cells and a novel role for antioxidants in the corpus luteum

During folliculogenesis the granulosa cells divide whilst in contact with each other, and so exhibit some of the characteristics of stem cells. In vitro we have shown that bovine granulosa cells from 3-7 mm follicles, like stem cells, divide without the need for a substratum, and produce colonies of cells. Growth factors, bFGF and IGF's, stimulate their division. These cells secrete and assemble a basal lamina, suggesting that the follicular basal lamina is produced by the granulosa cells. They have the morphological characteristics of follicular granulosa cells. Thus this system is ideal for studying the functions of immature granulosa cells because the cells do not spontaneously differentiate or luteinize into luteal cells, as occurs in culture on a substratum. On differentiation into luteal cells in vivo the cells express the steroidogenic enzymes for progesterone production and accumulate beta-carotene. During culture of bovine luteal cells we observed that a proportion of the steroidogenic enzyme cholesterol side-chain cleavage cytochrome P450 enzyme became chemically cross-linked to its electron donor, adrenodoxin. P450 enzymes produce oxygen free radicals and oxygen free radicals can cause cross-linking between proteins in close proximity. Cell protect against this damage by the use of antioxidant vitamins. Repleting the cultured luteal cells with beta-carotene reduced the amount of cross-linking. We conclude that the high levels of beta-carotene in corpora lutea are to protect against damage due to oxygen free radicals generated in the course of progesterone synthesis.

Anchorage-independent culture of bovine granulosa cells: the effects of basic fibroblast growth factor and dibutyryl cAMP on cell division and differentiation

During ovarian folliculogenesis granulosa cells divide while in contact with stromal cells and other granulosa cells. Following ovulation, however, they cease dividing and differentiate into large luteal cells. When cultured in monolayer, granulosa cells spontaneously differentiate into luteal cells, thus confounding the study of the follicular functions of granulosa cells in vitro, such as cell division. We have found that bovine granulosa cells were able to divide in an anchorage-independent culture system consisting of soft agar and an overlay of methylcellulose. The cells grew in colonies and retained the ultrastructural features of follicular granulosa cells. They also secreted an extracellular matrix with features of basal lamina. The granulosa cells responded to basic fibroblast growth factor (bFGF) in a dose- and time-dependent manner, with a three- to five-fold increase (at 50 ng bFGF/ml for 14 days) in the level of DNA per dish. This mitogenic effect was inhibited by dibutyryl cAMP (dbcAMP) (1 mM). In the presence of dbcAMP the cells hypertrophied considerably, did not secrete extracellular matrix, and developed the ultrastructural features of luteal cells. They also secreted threefold more progesterone. This system offers the ability to study the follicular functions of granulosa cells in culture.

Altered intestinal development after jejunal ligation in fetal sheep

Experimental obstruction of the fetal small intestine resulted in massive hypertrophy of the segment proximal to the site of obstruction. Villus morphology was grossly abnormal. Enterocytes developed many irregular features, most notably cytoplasmic extensions (pseudopods, or blebs) from their apical surface. Distal to the site of obstruction, morphological anomalies which resembled those seen after experimental oesophageal ligation were found. These included delayed disappearance of the apical endocytic network, disrupted or absent microvilli, glycogen accumulation and inappropriate cell extrusion. Proximal to the obstruction, where stasis of swallowed fluid occurs, distension and abnormal intestinal development ensues. Distal to the obstruction where the intestine develops in the absence of swallowed fluid, development is also abnormal. The anomalies resemble those noted after oesophageal ligation in utero, and possibly are the results of reduced cellular nutrition. These results suggest that fetal ingestion provides the developing gastrointestinal tract with an important stimulus for normal growth.

Effect of additives on the crystallization of glutamate dehydrogenase from Clostridium symbiosum

A new crystal form of the hexameric NAD(+)-linked glutamate dehydrogenase (GDH) from Clostridium symbiosum has been grown using the hanging drop method of vapour diffusion. The crystals are obtained either by using high concentrations of the amino acid substrate of the enzyme, glutamate, as the precipitant or by co-crystallization from ammonium sulphate in the presence of either p-chloromercuribenzene sulphonate or potassium tetracyanoplatinate. The crystals diffract well and X-ray photographs have established that they are in the space group R32. Considerations of the values of Vm indicate that the asymmetric unit of the R32 crystals contains a single subunit. Packing considerations based on the structure of the native enzyme determined from a different crystal form suggest that the molecule must undergo a significant conformational change in order to be accommodated in the new cell. Such a conformational rearrangement may represent an important step in the catalytic cycle.

Glucocorticoid effects on rabbit fetal lung maturation in vivo: an ultrastructural morphometric study

Maternal administration of glucocorticoids is known to stimulate fetal lung maturation. In the present study, we used microscopy and stereology to evaluate the morphological effects of maternal glucocorticoid treatment on rabbit fetal lung tissue. Betamethasone was administered to pregnant rabbits on days 25 and 26 of gestation at a dose of 0.2 mg/kg body weight. The animals were sacrificed on day 27 of gestation. Glucocorticoid treatment significantly increased the presumptive airspace in the fetal lung tissue but did not alter the relative proportion of epithelium, connective tissue, or vasculature in the tissue. In addition, glucocorticoid treatment significantly increased the proportion of type II cells in the prealveolar epithelium, increased the rate of phosphatidylcholine synthesis, and increased the content of the major surfactant-associated protein, SP-A, in the fetal lung tissue. We could detect no effect of betamethasone on lamellar body cross-sectional area, numerical density, or volume density within fetal lung type II cells. Glucocorticoid treatment of the pregnant doe caused a decrease in the volume density of intracellular glycogen and an increase in the volume density of mitochondria in fetal lung type II cells. Betamethasone treatment did not alter the distance between fetal lung epithelial cells and subadjacent connective tissue cells. However, glucocorticoid treatment increased the number of connective tissue foot processes that pierced the epithelial basal lamina. Thus, glucocorticoid treatment of the pregnant doe results in structural changes in the fetal lung tissue, an acceleration of some aspects of type II cell differentiation, and a concomitant increase in epithelial-mesenchymal interactions.

Use of chemical modification in the crystallization of isocitrate lyase from Escherichia coli

Two different crystal forms of isocitrate lyase (ICL) from Escherichia coli have been grown following the chemical modification of the enzyme by either 3-bromopyruvate or ethyl mercuri thiosalicylate (EMTS), contrasting strongly with difficulties in obtaining ordered crystals of the native enzyme. Both crystal forms are obtained using the hanging drop method of vapour diffusion with ammonium sulphate as the precipitant. The crystals diffract well and X-ray photographs of the crystals have established that they are in space groups C222(1) and P3(1) (or its enantiomorph P3(2), respectively. Considerations of the values of Vm and measurements on the crystal density indicate that the asymmetric unit of both crystals contains four subunits.

Uptake of the 35 kDa major surfactant apoprotein (SP-A) by neonatal rabbit lung tissue

Secreted surfactant is made up of both phospholipid and protein components. Therefore, we investigated the possibility that surfactant apoproteins might be taken up by the alveolar type II cell in a manner similar to the uptake of surfactant phosphatidylcholines. Day 2 neonatal rabbits were infused via the trachea with a solution of carrier surfactant and 125I-labelled surfactant apoprotein (SP-A, Mr approx. 35,000). Most of the 125I-SP-A remained within the alveolus; however, a fraction of the 125I-SP-A was taken up by the lung tissue from the alveolus in a time-dependent manner. The small amount of radiolabeled material detected in blood, liver or kidney tissues of 125I-SP-A-infused animals was not trichloroacetic acid (TCA) precipitable, i.e., probably represented degradation products. In contrast, the proportion of TCA-precipitable 125I-SP-A in lung tissue or lavage samples did not change as function of time after tracheal administration. Two-dimensional gel electrophoresis of the 125I-SP-A present in the lavage samples or associated with lung tissue was used to show that a small proportion of the 125I-SP-A was partially degraded in the lung tissue and alveolus. These data are suggestive that the SP-A is taken up by lung tissue, perhaps in a manner similar to the uptake of surfactant phospholipid by the alveolar type II cell.

Microscopic study of cortical explants from lamb kidney in culture

Cortical explants from lamb kidney have been maintained in organ culture for up to 12 days. Early in culture, the tissue showed limited necrosis, but most tissue elements, especially those closest to the medium, significantly recovered by day 5. Glomerular peripolar cells were present for at least the first 3 days of culture. Neotubular formation was noted by day 5, often appearing as cyst-like structures. Glomerular podocytes lost their foot processes early in culture but apparently remained viable throughout the total culture period.

Localization and accumulation of fibronectin in rabbit fetal lung tissue

An interaction between mesenchyme and epithelium is required for the normal differentiation of fetal lung tissue. This morphogenic interaction may be mediated, in part, by changes in the composition and/or structure of the extracellular matrix. Therefore, we characterized the localization and accumulation of fibronectin, an extracellular-matrix component, during several stages of lung development in the rabbit fetus in vivo as well as in day-21 rabbit fetal lung explants maintained in vitro. Fibronectin was detected immunocytochemically in the basement-membrane zone beneath the epithelial ducts in lung tissue obtained from rabbit fetuses at 19 and 21 days of gestation. In fetal lung tissue obtained at these early stages of lung development, mesenchymal cells were stained only at their periphery. Immunostaining for connective-tissue fibronectin increased greatly between days 24 and 31 of gestation. A similar increase in the intensity of immunostaining for connective-tissue fibronectin was observed in rabbit fetal lung explants that had been maintained in vitro for 7 days. The concentration of fibronectin in fetal lung tissue obtained at different days of gestation was determined using a specific enzyme-linked immunoadsorbent assay (ELISA) and was found to increase from 1.7 ng/micrograms protein in fetal lung tissue obtained at day 19 of gestation to 7.3 ng/micrograms protein in fetal lung tissue obtained at day 24 of gestation. The levels of fetal lung fibronectin then remained relatively constant through to day 31 of gestation. A similar increase in fibronectin concentration was observed in day-21 fetal lung explants maintained in vitro for 7 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunolocalization of cholesterol side-chain-cleavage cytochrome P-450 and ultrastructural studies of bovine corpora lutea

Corpora lutea were collected from cows at four stages of the luteal phase and prepared for immunostaining at the light microscope level. Other corpora lutea, which were fully developed, were dispersed by collagenase treatment and freshly isolated and cultured cells were processed for immunostaining. Electron microscopy was carried out on mature corpora lutea and freshly isolated cells. Positive staining for cholesterol side-chain-cleavage cytochrome P-450 (P-450scc), an inner-mitochondrial membrane enzyme considered to catalyse the rate-limiting step in the conversion of cholesterol to progesterone, was observed in all corpora lutea. The intensity of staining was much greater in mature corpora lutea than in young or regressing corpora lutea. Only small and large luteal cells stained positively and cells of the vasculature and other connective tissue elements did not. When cells were cultured and had become flatter, the intensity of immunostaining was observed to be greater in large luteal cells than in small luteal cells which was interpreted to be due, in part, to the greater volume density of mitochondria in these cells. In some cultured small luteal cells the pattern of immunostaining appeared as whorls of strands encircling the nucleus. This pattern was interpreted as a three-dimensional network of mitochondria organized into 'strands', more than one mitochondrion in cross-section, perhaps formed during the process of attachment and elongation of the cells. Further observations made at the electron microscope level, included the presence of close (5-8 nm) contacts with interconnecting septa between small luteal cells in tissue.

Immunolocalization of cholesterol side-chain-cleavage cytochrome P-450 and 17 alpha-hydroxylase cytochrome P-450 in bovine ovarian follicles

Follicles were collected from cows and processed for electron microscopy and for immunofluorescent staining at the light microscope level. Key regulatory steroidogenic enzymes cholesterol side-chain-cleavage cytochrome P-450 (P-450scc) and 17 alpha-hydroxylase cytochrome P-450 (P-45017 alpha) were immunolocalized using specific IgG fractions raised against these enzymes. In larger follicles in which the theca interna had differentiated, positive staining for cytochromes P-450scc and P-450(17) alpha was observed in the cells of the theca interna. Electron microscopic examination showed that these cells were rich in endoplasmic reticulum, mainly rough, and had moderate numbers of mitochondria with tubular and lamellar cristae. Positive staining was also present in the theca of follicles undergoing atresia. Positive staining for cytochrome P-450(17) alpha was not observed in the membrana granulosa but cytochrome P-450scc was present in the membrana granulosa in some follicles, particularly in the larger antral follicles. By contrast, positive staining for both enzymes was not observed in stroma, surface epithelium or in small preantral follicles in which the theca interna had not differentiated. These results indicate good agreement between the type(s) of steroidogenic enzyme(s) present in tissues and the type(s) of steroid hormone(s) produced. It is concluded that regulation of steroid hormone production involves, at least in part, regulation of the levels of steroidogenic enzymes.