Photoinduced Coupling of Acetylenes and Quinone in the Solid State as Preorganized Donor-Acceptor Pairs

Crystalline electron donor-acceptor (EDA) complexes of various diarylacetylenes (DA) and dichlorobenzoquinone (DB) are isolated and structurally characterized by X-ray crystallography. Deliberate excitation of either the DB acceptor at lambda(DB) = 355 nm or the 1:2 [DA, 2DB] complex at lambda(CT) = 532 nm in the solid state leads to [2 + 2] cycloaddition and identical (isomeric) mixtures of the quinone methide products. Time-resolved (ps) diffuse reflectance spectroscopy identifies the ion-radical pair [DA(*+), DB(*-)] as the reactive intermediate derived by photoinduced electron transfer in both photochemical procedures. The effects of crystal-lattice control on the subsequent ion-radical pair dynamics are discussed in comparison with the same photocouplings of acetylenes and quinone previously carried out in solution.

HLA class I and class II DNA typing and the origin of Basques

Seven HLA class I and class II loci (HLA-A, B, C, DRB1, DQA1, DPA1 and DPB1) were typed at the DNA level in two populations of the Iberian Peninsula (100 Basque and 88 Catalan individuals) in order to unravel their genetic relationship and to compare these results with other European and Mediterranean populations. For the first time, the frequencies of alleles and haplotypes for the class I HLA loci at the DNA level in these populations are presented. The most frequent haplotype in both populations is A*29-Cw*1601-B*44-DRB1*0701-DQA1*0201-DPA1*0103-DPB 1*0401. Neither population differed markedly from the highly homogeneous European and Mediterranean genetic landscape. The Basques, a European outlier population according to classical genetic markers, appear to lie within the genetic European variation with a slight uniqueness and show no clear relationship to North African populations, as has been postulated in some previous HLA studies. Here, the range of possibilities provided by the highly polymorphic HLA system is stressed by using genetic distances, phylogenetic trees and principal component analyses in order to reconstruct population history.

Scoliosis in elderly and age-related bone loss: a population-based study

Osteoporosis, a common metabolic condition resulting in reduced bone mass, causes significant morbidity in affected individuals by predisposing them to osteoporotic fractures. To determine the relationship of scoliosis and osteoporosis, dual-energy X-ray absorptiometry (DXA) scans of 493 men and 762 women were analyzed according to their scoliotic status. No association was observed in the few scoliotic men without osteoarthritis of the spine compared to nonscoliotic men. Without osteoarthritis, scoliotic women had significantly decreased bone mass of the total hip and the femoral neck (p < 0.05) compared to nonscoliotic women, whereas in spine, bone mass was also decreased compared to nonscoliotic women, but not statistically significant. This suggests that scoliosis associates with bone loss, and affected women may benefit from early institution of therapeutic measures.

Normal regional anatomy of the shoulder

The shoulder is a remarkable structure enjoying a greater range of motion than any other articulation in the human body. The shoulder is not a single joint but actually four separate articulations that act synergistically. The authors review the complex anatomy of the shoulder, presenting correlation between anatomic sections and MR arthrography.

Raf-induced proliferation or cell cycle arrest is determined by the level of Raf activity with arrest mediated by p21Cip1

The Raf family of protein kinases display differences in their abilities to promote the entry of quiescent NIH 3T3 cells into the S phase of the cell cycle. Although conditional activation of deltaA-Raf:ER promoted cell cycle progression, activation of deltaRaf-1:ER and deltaB-Raf:ER elicited a G1 arrest that was not overcome by exogenously added growth factors. Activation of all three deltaRaf:ER kinases led to elevated expression of cyclin D1 and cyclin E and reduced expression of p27Kip1. However, activation of deltaB-Raf:ER and deltaRaf-1:ER induced the expression of p21Cip1, whereas activation of deltaA-Raf:ER did not. A catalytically potentiated form of deltaA-Raf:ER, generated by point mutation, strongly induced p21Cip1 expression and elicited cell cycle arrest similarly to deltaB-Raf:ER and deltaRaf-1:ER. These data suggested that the strength and duration of signaling by Raf kinases might influence the biological outcome of activation of this pathway. By titration of deltaB-Raf:ER activity we demonstrated that low levels of Raf activity led to activation of cyclin D1-cdk4 and cyclin E-cdk2 complexes and to cell cycle progression whereas higher Raf activity elicited cell cycle arrest correlating with p21Cip1 induction and inhibition of cyclin-cdk activity. Using green fluorescent protein-tagged forms of deltaRaf-1:ER in primary mouse embryo fibroblasts (MEFs) we demonstrated that p21Cip1 was induced by Raf in a p53-independent manner, leading to cell cycle arrest. By contrast, activation of Raf in p21Cip1(-/-) MEFs led to a robust mitogenic response that was similar to that observed in response to platelet-derived growth factor. These data indicate that, depending on the level of kinase activity, Raf can elicit either cell cycle progression or cell cycle arrest in mouse fibroblasts. The ability of Raf to elicit cell cycle arrest is strongly associated with its ability to induce the expression of the cyclin-dependent kinase inhibitor p21Cip1 in a manner that bears analogy to alpha-factor arrest in Saccharomyces cerevisiae. These data are consistent with a role for Raf kinases in both proliferation and differentiation of mammalian cells.

Population genetics of Y-chromosome short tandem repeats in humans

Eight human short tandem repeat polymorphisms (STRs) also known as microsatellites-DYS19, DYS388, DYS390, DYS391, DYS392, DYS393, DYS389I, and DYS389II, mapping in the Y chromosome-were analyzed in two Iberian samples (Basques and Catalans). Allele frequency distributions showed significant differences only for DYS392. Fst and gene diversity index (D) were estimated for the Y STRs. The values obtained are comparable to those of autosomal STR if corrections for the smaller effective population size on the Y chromosome are taken into account. This suggests that Y-chromosome microsatellites might be as useful as their autosomal counterparts to both human population genetics and forensics. Our results also reinforce the hypothesis that selective sweeps in the Y chromosome in recent times are unlikely. Haplotypes combining five of the loci were constructed for 71 individuals, showing 29 different haplotypes. A haplotype tree was constructed, from which an estimate of 7,000 to 60,000 years for the age of the Y-chromosome variation in Iberia was derived, in accordance with previous estimates obtained with mtDNA sequences and nuclear markers.

Mutations of critical amino acids affect the biological and biochemical properties of oncogenic A-Raf and Raf-1

The catalytic domains of the Raf family of protein kinases (deltaRaf) differ in their ability to activate MEK in vitro and in vivo and in their ability to oncogenically transform mammalian cells. The kinase domain of B-Raf is more active than the equivalent portion of Raf-1 which in turn is more active than A-Raf. In Raf-1 the phosphorylation or mutation to aspartic acid of two key tyrosine residues upstream of the ATP binding site has been demonstrated to significantly potentiate catalytic activity. In A-Raf the analogous amino acids are also tyrosine whereas in B-Raf they are aspartic acid. To determine if these differences in amino acid sequence influence the relative catalytic activity of the Raf kinase domains we constructed forms of deltaA-Raf, deltaB-Raf and deltaRaf-1 that encode either aspartic acid [DD], phenylalanine [FF] or tyrosine [YY] at these positions. These proteins were expressed both in mammalian cells as fusions with the hormone binding domain of the estrogen receptor and as epitope-tagged proteins in Sf9 insect cells to test their oncogenic and catalytic potentials. When expressed in Rat1 or 3T3 cells in the presence of hormone all of the deltaRaf-1:ER and deltaA-Raf:ER proteins were transforming with the exception of the [FF] form of deltaA-Raf. In general the [DD] forms of the deltaRaf-1:ER and deltaA-Raf:ER proteins were the most potently oncogenic which correlated with their ability to elicit activation of the MAP kinase pathway. Consistent with the transformation data, the catalytic activity of the [DD] forms of deltaA-Raf:ER and deltaRaf-1:ER was about ten times greater than the cognate [FF] and [YY] forms of the proteins. By contrast all of the deltaB-Raf:ER proteins were highly transforming and deltaB-Raf catalytic activity was largely unaffected by mutation of the aforementioned aspartic acids to either tyrosine or phenylalanine. Similar results were obtained with epitope-tagged forms of deltaA-Raf, deltaB-Raf and deltaRaf-1 expressed in Sf9 cells. These data provide support for the model that key tyrosine residues in the protein kinase domains of A-Raf and Raf-1 are important in the regulation of catalytic activity. In addition they demonstrate that the higher intrinsic activity of B-Raf cannot be explained simply by the presence of aspartic acids at the analogous positions.

Allele frequencies for 20 microsatellites in a worldwide population survey

20 microsatellite polymorphisms: HUMHPRT, HUMD3S1358, HUMTH01, HUMACPP, HUMVWF, HUMD16S310, HUMD4S243, HUMTPO, HUMFES/FPS, HUMF13A1, HUMDHFRP2, HUMD11S2010, HUMD13S767, HUMD9S926, HUMD2S1328, HUMD14S306, HUMD18S848, HUMD5S818, HUMD7S820 and HUMFGA were analyzed in a worldwide survey covering five continents and allele frequencies are given. There is a high heterogeneity in allele frequencies among continents. A neighbor-joining tree based on Fst distance shows a pattern of differentiation that may reflect the role of drift in the development of genetic differences among humans. The variation found between continents confirms the usefulness of tetranucleotide microsatellites in human genetic variation studies.

Population history of north Africa: evidence from classical genetic markers

After an intensive bibliographic search, we compiled all the available data on allele frequencies for classical genetic polymorphisms referring to North African populations and synthesized the data in an attempt to reconstruct the populations' demographic history using two complementary methods: (1) principal components analysis and (2) genetic distances represented by neighbor-joining trees. In both analyses the main feature of the genetic landscape in northern Africa is an east-west pattern of variation pointing to the differentiation between the Berber and Arab population groups of the northwest and the populations of Libya and Egypt. Moreover, Libya and Egypt show the smallest genetic distances with the European populations, including the Iberian Peninsula. The most plausible interpretation of these results is that, although demic diffusion during the Neolithic could explain the genetic similarity between northeast Africa and Europe by a parallel process of gene flow from the Near East, a Mesolithic (or older) differentiation of the populations in the northwestern regions with later limited gene flow is needed to understand the genetic picture. The most isolated groups (Mauritanians, Tuaregs, and south Algerian Berbers) were the most differentiated and, although no clear structure can be discerned among the different Arab- and Berber-speaking groups, Arab speakers as a whole are closer to Egyptians and Libyans. By contrast, the genetic contribution of sub-Saharan Africa appears to be small.

Mitochondrial DNA variation and the origin of the Europeans

Sequences from the mitochondrial DNA (mtDNA) control region were analyzed in nine European and West Asian populations. They showed low genetic heterogeneity when compared to world populations. However, a Caucasoid population tree displayed a robust east-west gradient. Within-population diversity (ascertained through various parameters) and mean pairwise differences declined from east to west, in a pattern compatible with ancient population migration and expansion from the Middle East. Estimated expansion times indicate a Paleolithic event with important differences among populations according to their geographical position and thus a slower tempo than previously believed. The replacement of Neanderthals by anatomically modern humans, fully compatible with the present results, may have been a slower and more complex process than cultural change suggests.

Dysfunction of implantable defibrillators caused by slot machines

The electrogram storage is a feature offered by the last generation of defibrillators, which enables the physician to establish whether the sensed episode and the electrical therapy delivered by the device was appropriate. The incidence of electromagnetic interferences may be higher than initially suspected with the latest generation of defibrillators. Such interference was documented in 4 out of 100 patients over a 24-month period. The electrical interference occurred in all four of them, while they were playing with slot machines. In the RR interval history, irregular QRS sensing of variable frequency was documented in some episodes. The intervals were irregular and nonphysiological satisfying the rate cut-off criteria in an intermittent and nonsustained way. There may be high risk of electromagnetic interference between slot machines and defibrillators. Our experience calls for a warning to all defibrillator patients and, perhaps some regulatory intervention.

Unsharp masking of low-dosed digital luminescence radiographs: results of a receiver operating characteristics analysis

The extent to which the diagnostic performance of low-dosed storage phosphors can be improved by suitable image postprocessing was investigated. Storage phosphor radiographs and conventional 200- and 400-speed screen-film combinations of an anthropomorphic chest phantom with simulated nodules and linear structures were compared. The detection of test bodies was determined in a ROC analysis based on 16200 individual observations. The two analog screen-film systems did not differ significantly. As far as the storage phosphor radiographs are concerned, a higher diagnostic performance was achieved with a large filter kernel (S 40) whereas small filter kernels and edge-enhanced imaging modes reduced the detection of detail. The image quality of low-dosed storage phosphors is thus similar to high-amplification screen-film combinations if large filter kernels are used in postprocessing of the image.

The safety and effectiveness of stepwise and low-dose administration of follicle stimulating hormone in WHO group II anovulatory infertile women: evidence from a large multicenter study in Spain

PURPOSE

Our goal was to investigate the safety, effectiveness, and feasibility for the practicing physician of stepwise and low-dose administration of FSH in WHO group II anovulatory infertile women.

METHODS

Infertile female patients (n = 234) suffering from WHO group II anovulation, and who failed to became pregnant with clomiphene citrate, were included in a multicenter, prospective, clinical study of treatment with a protocol of chronic low-dose and small incremental rises with urinary purified or highly purified FSH. Follicular development was monitored with ultrasonographic scans.

RESULTS

The 234 patients received a total of 534 cycles of treatment, for a mean number of 2.3 treated cycles per patient. hCG was withheld in 65 (12.2%) cyles because of no response and in 28 (5.2%) cycles because of hyperresponse. Of the remaining 441 cycles, 419 (95%) were ovulatory, and in 198 (47.3%) of these cycles a single dominant follicle developed. There were 93 pregnancies (39.7% per patient), for a cycle fecundity rate of 17.4%. Cumulative conception rate after two treated cycles was 33.5%. There were 14 (15%) pairs of twins and 10 (10.8%) spontaneous miscarriages. The prevalence of complications was low with no cases of severe OHSS. Basal LH/FSH ratio was significantly higher in the pregnant group of patients than in nonpregnant women.

CONCLUSIONS

Stepwise and chronic low-dose administration of FSH is a safe and effective method for treatment of WHO group II anovulatory infertility, mainly in those patients having high LH/FSH ratios.

Conditionally oncogenic forms of the A-Raf and B-Raf protein kinases display different biological and biochemical properties in NIH 3T3 cells

The protein kinase domains of mouse A-Raf and B-Raf were expressed as fusion proteins with the hormone binding domain of the human estrogen receptor in mammalian cells. In the absence of estradiol, 3T3 and rat1a cells expressing delta A-Raf:ER and delta B-Raf:ER were nontransformed, but upon the addition of estradiol the cells became oncogenically transformed. Morphological oncogenic transformation was more rapid and distinctive in cells expressing delta B-Raf:ER compared with cells expressing delta A-Raf:ER. Biochemical analysis of cells transformed by delta A-Raf:ER and delta B-Raf:ER revealed several interesting differences. The activation of delta B-Raf:ER consistently led to the rapid and robust activation of both MEK and p42/p44 MAP kinases. By contrast, the activation of delta A-Raf:ER led to a weak activation of MEK and the p42/p44 MAP kinases. The extent of activation of MEK in cells correlated with the ability of the different Raf kinases to phosphorylate and activate MEK1 in vitro. delta B-Raf:ER phosphorylated MEK1 approximately 10 times more efficiently than delta Raf-1:ER and at least 500 times more efficiently than delta A-Raf:ER under the conditions of the immune-complex kinase assays. These results were confirmed with epitope-tagged versions of the Raf kinase domains expressed in insect cells. The activation of all three delta Raf:ER proteins in 3T3 cells led to the hyperphosphorylation of the resident p74raf-1 and mSOS1 proteins, suggesting the possibility of "cross-talk" between the different Raf kinases and feedback regulation of intracellular signaling pathways. The activation of either delta B-Raf:ER or delta Raf-1:ER in quiescent 3T3 cells was insufficient to promote the entry of the cells into DNA synthesis. By contrast, the activation of delta A-Raf:ER in quiescent 3T3 cells was sufficient to promote the entry of the cells into S phase after prolonged exposure to beta-estradiol. The delta Raf:ER system has allowed us to reveal significant differences between the biological and biochemical properties of oncogenic forms of the Raf family of protein kinases. We anticipate that cells expressing these proteins and other estradiol-regulated protein kinases will be useful tools in future attempts to unravel the complex web of interactions involved in intracellular signal transduction pathways.

Interpretation of abnormal lumbosacral spine radiographs. A test comparing students, clinicians, radiology residents, and radiologists in medicine and chiropractic

STUDY DESIGN

Controlled comparison of radiographic interpretive performance based on training and experience.

OBJECTIVES

This study compared each of these groups in medicine and chiropractic by testing abilities to interpret abnormal plain film radiographs of the lumbosacral spine and pelvis.

SUMMARY OF BACKGROUND DATA

Low back pain is a common and costly problem that is evaluated and treated primarily by medical physicians, orthopedists, and chiropractors. Although radiology is used extensively in patients with low back pain, the radiographic interpretations of students, clinicians, radiology residents, and radiologists have never been compared.

METHODS

Four hundred ninety-six eligible volunteers from nine target groups completed a test of radiographic interpretation consisting of nineteen cases with clinically important radiographic findings. The nine groups included 22 medical students, 183 chiropractic students, 27 medical radiology residents, 13 chiropractic radiology residents, 66 medical clinicians (including 12 general practice physicians, 25 orthopedic surgeons, 21 orthopedic residents, and 8 rheumatologists), 46 chiropractic clinicians, 48 general medical radiologists, 55 chiropractic radiologists, and 36 skeletal radiologists and fellows.

RESULTS

The test established a high level of internal consistency reliability (0.880) and revealed that, in the interpretation of abnormal plain film radiographs of the lumbosacral spine and pelvis, significant differences were found among professional groups (P < 0.0001). Post hoc tests (P < 0.05) revealed that skeletal radiologists achieved significantly higher test results than did all other medical groups; that the test results of general medical radiologists and medical radiology residents was significantly higher than those of medical clinicians; that test results of medical students was significantly poorer than that of all other medical groups; that the performance of chiropractic radiologists and chiropractic radiology residents was significantly higher than that of chiropractic clinicians and chiropractic students; that no significant differences was revealed in the mean values of performance of chiropractic clinicians and chiropractic students; that the test results of chiropractic radiologists, chiropractic radiology residents, and chiropractic students was significantly higher than that of the corresponding medical categories (general medical radiologists, medical radiology residents, and medical students, respectively); that no significant difference in test results was identified between chiropractic radiologists and skeletal radiologists or between chiropractic and medical clinicians; and that the length of time in practice for clinicians and radiologists was not a significant factor in the test results.

CONCLUSIONS

These data demonstrate a substantial increase in test results of all radiologists and radiology residents when compared to students and clinicians in both medicine and chiropractic related to the interpretation of abnormal radiographs of the lumbosacral spine and pelvis. Furthermore, the study reinforces the need for radiologic specialists to reduce missed diagnoses, misdiagnoses, and medicolegal complications.

The healed Segond fracture: a characteristic residual bone excrescence

This report describes the natural history of the Segond fracture and documents the radiographic appearance of the healed Segond fracture. The clinical and radiographic records of 129 patients with acute anterior cruciate ligament (ACL) injuries were reviewed. Four (3.1%) of these patients had Segond fractures. On follow-up radiographic examination, seven patients demonstrated a characteristic bone excrescence arising 3-6 mm inferior to the lateral tibial plateau. In four of the five patients for whom acute injury films were available this excrescence arose at the site of the earlier Segond fracture. Healing of such fractures is associated with a characteristic bone excrescence distinct from an osteophyte. This excrescence implies significant internal derangement of the knee.

Patterns of central acetabular osteophytosis in osteoarthritis of the hip

RATIONALE AND OBJECTIVES

The frequency and morphology of central acetabular osteophyte formation were evaluated in patients with osteoarthritis.

METHODS

One hundred preserved acetabular specimens were evaluated for the occurrence of central osteophytes (excrescences present in the articulation of the hip joint), their relationship to marginal and femoral osteophytes of the hip, and their radiographic appearance.

RESULTS

In both specimen and patient analysis, the authors found that central excrescences occur commonly and appear to be related temporally to osteophytes of the femur and the margin of the acetabulum.

CONCLUSIONS

The authors demonstrated a close relationship between the degree of marginal and femoral osteophytes with those found centrally, indicating a temporal relationship. The new radiographic signs discussed are: 1) a fine linear density associated with early osteoarthritis; 2) larger, more irregular densities associated with a more advanced stage of osteoarthritis; and 3) obliteration of the acetabular fossa by excrescences as found in severe osteoarthritis.

Normal regional anatomy of the shoulder

The shoulder joint is a remarkable structure enjoying a greater range of motion than any other articulation in the human body. The shoulder is not a single joint but actually four separate articulations that act synergistically. The authors review the complex anatomy of the shoulder.

Phagocytosis of outer segments by retinal pigment epithelium: phagosome-lysosome interaction

We studied phagocytosis of rod outer segments (ROS) by the retinal pigmented epithelium (RPE) using rapid freezing, freeze-drying, and electron microscopic immunocytochemistry. Phagocytosis of photoreceptor outer segment tips by the RPE occurs daily, and in rats the shedding of these tips is light-entrained to a circadian rhythm. We studied the phagocytic process 5, 30, 90, and 150 min after light onset or after subjective light onset in rats entrained to a 12-hr dark-12-hr light cycle. Lysosomes were labeled with antibodies to cathepsin D, a major lysosomal enzyme responsible for opsin degradation. Phagosomes and phagolysosomes were recognized because of the lamellar structure of their photoreceptor-derived contents. We found a population of lysosomes that fuse with one another before they interact with phagosomes. This fusion can be triggered either by light or by endogenous circadian mechanisms. We also found that lysosome-phagosome interaction occurs after the ingestion stage is completed and that this interaction occurs in two steps. First, smaller lysosomes fuse with phagosomes. Subsequently, larger lysosomes appear to interact with phagosomes via pore-like or bridge-like structures. It is proposed that interchange of contents takes place through these structures.

Difficult-to-Detect Osseous Injuries

In brief MRI can prove diagnostically brief useful for a number of osseous injuries that active patients may incur. The authors weigh the benefits of MRI, such as early injury detection and excellent contrast and spatial resolution, versus its shortcomings, such as high cost and sensitivity to motion. In addition, they describe in detail the MRI appearances of stress fractures, bone bruises, occult fractures, and osteochondral fractures.

[A comparative study of intravenous diltiazem and nitroglycerin in the treatment of unstable angina]

To compare the efficacy of intravenous diltiazem vs nitroglycerin in patients with unstable angina, we conducted a prospective, single blinded study enrolling 45 patients, 24 of them received diltiazem and 21 nitroglycerin. We considered drug failure if the patient experienced two or more anginal episodes or if one of them was longer than 30 minutes. There was a good response in 19 of 24 patients (79%) of the diltiazem group and 17 of 21 (81%) in the nitroglycerin group. Only one of the 5 non-response patients in the diltiazem group that was crossed to nitroglycerin was controlled, in opposition to the 4 patients crossed to diltiazem that were controlled all of them (p less than 0.05). Both drugs significantly (p less than 0.01) reduced systolic and diastolic blood pressure, but there was not difference between the two groups. Heart rate and double product decreased only in the diltiazem group (p less than 0.05). We did not find notorious side effects. We concluded that diltiazem is an alternative to nitroglycerin in patients with unstable angina.

[Digital luminescence radiography (DLR) for skeletal diagnosis in traumatology]

170 patients who had suffered trauma to bones or soft tissues were examined by a digital and a conventional film/screen technique. In addition to "standard" and edge-enhanced images, post-processing was carried out and compared with conventional radiographs. Four radiologists and two surgeons evaluated the compacta, spongiosa, soft tissues, fractures and osteo-synthetic materials as shown on the two systems. The "standard" digital images are inferior to film images, but edge-enhanced images showed definite advantages for demonstrating soft tissues. Evaluation of osteo-synthetic material is limited by the creation of artifacts. Recognition of detail can be significantly improved by using post-processing with optimized parameters.

Ultrastructure of the electrotonic and chemical components of the lateral-to-motor and medial-to-motor synapses in crayfish nerve cord

Lateral-to-motor and medial-to-motor synapses in crayfish nerve cords are composed of an electrical and a chemical component. The presynaptic terminals showed localized clusters of synaptic vesicles, electron-dense areas, coated pits, and coated vesicles. In thin sections, active zones were defined by electron-dense regions where synaptic vesicles attached and, in freeze-fracture replicas, by clusters of intramembrane particles localized in bands with vesicle openings on the sides of these bands. The cytoplasmic surface of the postsynaptic membrane opposite the active zones was coated with electron-dense material that in freeze-fracture replicas was seen as an increase in intramembrane particles located in the external leaflet (EF-face). This specialization of the postsynaptic membrane may correspond to the neurochemical receptor. Also, pre- and postsynaptic membranes were separated by a wider extracellular gap than those of adjacent nonsynaptic regions and electrical synapses or gap junctions. Synaptic vesicles were located exclusively at the synaptic regions by means of a cytoskeleton that was different for the electrical and the chemical components. The vesicles associated with the electrical component were anchored to a cytoskeleton composed of a beaded layer of densities located parallel to the membrane. This cytoskeleton maintained the synaptic vesicles separated from the presynaptic membrane by a distance of 13 +/- 2 nm. The synaptic vesicles associated with the chemical component were anchored to electron-dense regions formed by filaments arranged in bundles, anchored to the presynaptic membrane. Vesicles lined both sides positioned to discharge their contents into the extracellular space and to replace the discharged vesicles.

Comparative study of neuronal and glial gap-junctions in crayfish nerve cords

Electrical synapses (neuronal gap-junctions) and glial gap-junctions were compared by using thin sectioning, freeze fracturing, and negative staining techniques. Neuronal and glial gap-junctions differed in the length of the extracellular domains of the channels, in the presence of a cytoskeleton associated to neuronal gap-junctions, and in their unit cell dimensions. The difference in length of the channels and the fact that both glial and neuronal gap-junctions had the same particle diameter suggest that the proteins forming glial and neuronal gap-junctions might have different molecular weights. The cytoskeleton associated to neuronal gap-junctions consisted of a beaded layer of densities located parallel to the membrane in the synaptic regions. Synaptic vesicles associated to neuronal gap-junctions were attached to this cytoskeleton, which was in turn anchored to the synaptic membrane through densities about 20 nm apart, a spacing similar to the neuronal unit cell dimension. These results suggest that the cytoskeleton might be responsible for the association of vesicles to neuronal gap-junctions and for maintaining the crystalline appearance of neuronal gap-junctions in situ.

Basal prolactin and the behaviour of the gonadotrophins, testosterone, androstenedione, estradiol, and the sex-hormone-binding globulin during stimulation with clomiphene in subjects with spermatogenic disorders

To clarify the significance of clomiphene test in spermatogenic disorders, it was performed on three groups of subjects: 10 with normozoospermia, 29 with oligozoospermia, and 11 with azoospermia. Two basal blood samples were drawn five days apart; prolactin, FSH, LH, estradiol, testosterone, androstenedione and sex-hormone-binding globulin were determined. 100 mg of clomiphene per day were administered for eleven consecutive days; another sample was drawn on the eleventh day and all the basal parameters, except prolactin, were determined. It may be concluded from the results: a) All the parameters studied increased significantly after clomiphene; and b) Testosterone levels obtained after clomiphene, as well as the increases in this hormone during the test and the ratio delta T/delta LH, were significantly lower in the oligozoospermic group. This finding suggests a decrease in the testicular androgenic function of this group.