Genetic interaction between shibire and comatose mutations in Drosophila suggest a role for snap-receptor complex assembly and disassembly for maintenance of synaptic vesicle cycling

NSF is an ATPase required for the fusion of secretory vesicles with plasma membrane. Conditional comatose (Drosophila homolog of N-ethylmaleimide sensitive fusion factor (NSF)) mutations in Drosophila block synaptic transmission at restrictive temperature. Current models hold that NSF-mediated dissociation of SNARE (SNAp REceptor) complexes on mature synaptic vesicles primes them for exocytic release. Paralysis in comt mutants thus reflects defective exocytosis due to buildup of unresolved SNARE complexes. Here, we analyze effects of blocking synaptic vesicle recycling on behavioral, physiological and biochemical phenotypes of comt. Behavioral recovery of comt animals and recovery of comt synapses, as assayed by electroretinograms, after exposure to high temperature is faster if synaptic vesicle recycling is simultaneously blocked using shi(ts) mutants. Concurrently, 7S complex buildup in comt shi double mutants is substantially lower than in comt mutants alone. In addition, we find that 7S complexes can form on presynaptic plasma membrane if NSF is inhibited after synaptic-vesicle depletion. Thus, our experiments demonstrate a need for continuous NSF activity required not only for dissociating cis-SNARE complexes on plasma membrane after exocytosis, but also for maintaining these cis-SNARE complexes in a dissociated state.

Tyrosine residues 951 and 1059 of vascular endothelial growth factor receptor-2 (KDR) are essential for vascular permeability factor/vascular endothelial growth factor-induced endothelium migration and proliferation, respectively

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) exerts its multiple functions by activating two receptor tyrosine kinases, Flt-1 (VEGFR-1) and KDR (VEGFR-2), both of which are selectively expressed on primary vascular endothelium. To dissect the respective signaling pathways and biological functions mediated by these receptors in primary endothelial cells with two receptors intact, we, recently developed chimeric receptors (EGDR and EGLT) in which the extracellular domain of the epidermal growth factor receptor was fused to the transmembrane domain and intracellular domain of KDR and Flt-1, respectively. With these fusion receptors, we have shown that KDR is solely responsible for VPF/VEGF-induced human umbilical vein endothelial cell (HUVEC) proliferation and migration, whereas Flt-1 showed an inhibitory effect on KDR-mediated proliferation but not migration. To further characterize the VPF/VEGF-stimulated HUVEC proliferation and migration here, we have created several EGDR mutants by site-directed mutagenesis. We show that tyrosine residues 1059 and 951 of KDR are essential for VPF/VEGF-induced HUVEC proliferation and migration, respectively. Furthermore, the mutation of tyrosine 1059 to phenylanaline results in the complete loss of KDR/EGDR-mediated intracellular Ca(2+) mobilization and MAPK phosphorylation, but the mutation of tyrosine 951 to phenylanaline did not affect these events. Our results suggest that KDR mediates different signaling pathways for HUVEC proliferation and migration and, moreover, intracellular Ca(2+) mobilization and MAPK phosphorylation are not essential for VPF/VEGF-induced HUVEC migration.

Lethal comatose mutation in Drosophila reveals possible role for NSF in neurogenesis

NSF is a cytosolic ATPase implicated in a variety of cellular functions including synaptic vesicle exocytosis. Here we report a lethal mutation in the Drosophila homolog of NSF (dNSF1). Lethality staging and rescue experiments with the wild type dNSF1 transgene show that NSF1 is critically required during early larval stages and during late pupariation. Lethality in larval stages is associated with defects in neurogenesis as evidenced by an overall reduction in synapse size and synapse branching. Moreover, escaper adults, though showing abnormal seizure-like paralytic behavior, are normal in terms of synaptic transmission as assayed by electroretinograms. Taken together, these data indicate a role for NSF in neural growth and branching in addition to its documented role in synaptic transmission.

High focal depth with a quasi-bifocus birefringent lens

The Strehl definition along the axis of a birefringent lens sandwiched between two polarizers is studied analytically. The optic axis of the birefringent lens made of a uniaxial crystal is perpendicular to the lens axis, and the system behaves like a bifocus lens for proper orientation of the polarizers. The Sparrow criterion is employed for designing an imaging system with high depth of focus. It is shown that, when the two foci are separated by the Sparrow limit of resolution, the focal depth is maximum and the intensity point-spread function remains almost identical within this limit. The resolution according to the Rayleigh criterion in this zone is more than that of an ideal lens.

Phenotypic interaction between temperature-sensitive paralytic mutants comatose and paralytic suggests a role for N-ethylmaleimide-sensitive fusion factor in synaptic vesicle cycling in Drosophila

The temperature-induced paralysis of comatose (comt) mutants of Drosophila is suggestive of a function for N-ethylmaleimide-sensitive fusion factor (NSF) in the CNS. Mutations in the para gene encoding the subunit of the voltage-gated sodium channel also result in a similar phenotype. We show that paralysis in comt flies is activity-dependent, and in the doubly mutant comt para flies comt-like paralysis does not set in until the effects of para are reversed by shifting to permissive temperatures. During recording from the thoracic flight muscles, we observed that comt flies showed a burst of spontaneous activity at restrictive temperature. This has been reported earlier as a unique characteristic of comt paralysis. The comt para double mutant showed this burst of activity not at restrictive but only on shifting back to permissive temperature. The unusual behavior and electrophysiology of the doubly mutant flies reported here indicates a role for NSF in synaptic vesicle cycling.

Initial microbiologic studies did not affect outcome in adults hospitalized with community-acquired pneumonia

Microbiologic studies (MBSs) fail to identify a specific pathogen in more than 50% of patients with community-acquired pneumonia (CAP). The 1993 American Thoracic Society guideline (ATS-GL) for the management of CAP advised selecting initial antibiotic regimens based on severity of illness and comorbidities. Our study evaluated the role of initial MBS in adult patients hospitalized with CAP and treated according to the ATS-GL. In 184 patients hospitalized at our facility for CAP in 1996, and treated according to the ATS-GL, 25 (14%) failed to respond to initial antibiotic regimens. In these nonresponders, there was no difference in mortality between those in whom antibiotics were changed empirically, and those with MBS-guided changes. We conclude that initial MBS may not be warranted in many adult patients admitted for CAP. Exceptions include patients with conditions that predispose to less common, more resistant pathogens.

Dopamine D2 and D4 receptor ligands: relation to antipsychotic action

Since the discovery that the antipsychotic action of phenothiazines was mediated by dopamine D2 receptors, the dopamine system has been scrutinized for schizophrenia related abnormalities. The focus has been to create neuroleptics with improved antipsychotic profiles and reduced side effects. With the identification of multiple dopamine receptor subtypes, the hypotheses regarding the role of dopamine in schizophrenia and antipsychotic action of neuroleptics have been refined. Even after the molecular identification of newer dopamine D2-like receptor subtypes (D3 and D4), the dopamine D2 receptor is still considered the predominant site for antipsychotic action. However, there has been much debate concerning the modulatory role of other dopamine receptor sites in the mechanism of action of antipsychotic drugs. Specifically, the dopamine D4 receptor has received much attention in this regard, since the atypical antipsychotic agent, clozapine, preferentially blocks this receptor subtype as compared with dopamine D2 and D3 receptors. In this review we will highlight some of the observations and arguments regarding the involvement of the dopamine D2 and D4 receptor sites in the therapeutic efficacy of antipsychotic medication.

Humoral immunity status in neonates born to pre-eclamptic toxaemia mothers

A prospective study on 90 neonates born to age matched normal mothers (set I) and mothers (set II) with pre-eclamptic toxaemia (PET) was undertaken to assess and compare the humoral immunity status of the neonates. All of them had normal vaginal delivery. IgG, IgA and IgM were estimated by radial immunodiffusion technique from cord blood of neonates. It was observed that IgA and IgM levels were insignificant in the cord blood. IgG level was low in normal birth weight (NBW) neonates born to PET mothers, when compared to that of NBW neonates born to normal mothers. Again low birth weight (LBW) babies of both the sets showed lower values of IgG than that of NBW babies. Apgar scoring showed direct relationship with IgG levels e.g., higher the Apgar score higher the level of IgG. Thus the IgG level was directly related to the birth weight of the neonates of the respective sets as well as with the Apgar scoring of the neonates.

Is nitroglycerin detrimental in patients with coronary artery ectasia? A case report

During the management of acute myocardial infarction, we observed that clinical and electrocardiographic indications of myocardial ischemia worsened upon nitroglycerin infusion and were promptly relieved upon streptokinase infusion. Subsequent coronary angiography revealed diffuse ectasia with no significant stenosis. We discuss the possible pathophysiologic mechanisms by which nitroglycerin might exacerbate ischemia in patients with non-stenotic ectasia, and we present supporting data from other sources. We also attempt to identify the characteristics of patients whose acute myocardial ischemia might be worsened by the administration of nitroglycerin.

Pre-labour rupture of membrane: the histological study of membrane and bacteriological profile

One hundred two (102) cases of pre-labour rupture of membrane (PROM) were studied and special attention was given to the histological study of the amniotic membrane as well as to the bacteriological study of high vaginal flora, cervical flora and flora of amniotic fluid, in search of probable causes or factors leading to PROM. The incidence was found to be 3.16% in the age group of 20-25 years without any relation to parity; and the duration of gestation was 38 to 40 weeks in most of the cases. The histological study revealed: (a) Focally denuded amniotic epithelium, focally separated amniotic epithelium from chorion layer, lesser density of focal squamoid change of the epithelium and thicker chorion layer probably indicating focal immaturity of the chorio-amnion, (b) lesser thickness of collagen layer, focal hydropic degeneration and mild cellular infiltrate, (c) presence of focal hyaline degeneration and focal calcification of chorio-amnion. Microbial culture revealed: (a) Higher rate of positive culture in high vaginal swab, cervical swab and amniotic fluid showing presence predominantly of Esch coli, Strept haemolyticus, klebseilla species, Staph aureus, Strept non-haemolyticus, proteus species and pseudomonas species against that of positive cultures in the control cases, (b) no anaerobic bacteria from high vaginal swab, cervical swab or from amniotic fluid. It was presumed that focal immaturity of chorio-amnion or focal irregularity in the chorio-amnion at the microscopical level, focal degeneration of collagen superadded with bacterial infection, however mild, could be the factors leading to weakness in the tensile strength of chorio-amnion, again leading to PROM, in the face of stress factors of foetal origin.

A modification of split-skin graft

A modification of the conventional split-skin graft is presented. This modification provides a gain in the length of the donor skin up to a maximum of 1:1.92. The gain in length is achieved in a very short period during an emergency operation. No special instrument is required. This technique has been proved to be useful in burn cases having much less donor site than recipient area. Earlier recovery, shortened hospital stay, earlier rehabilitation, less scar contracture and less morbidity could be achieved with this type of simple modification of a sheet graft.

A comparative study of silver binding nucleolar organiser regions (AgNORs) of breast lesions in histological sections and fine needle aspiration smears

The study presents a comparative profile of AgNOR dot counting in different types of breast lesions in histopathological (HP) sections and fine needle aspiration cytology (FNAC) smears. The breast lesions chosen were non-neoplastic lesion like fibroadenosis, benign neoplastic lesion like fibroadenoma and malignant neoplastic lesion like infiltrating duct carcinoma-grade 2. The AgNOR counts of non-neoplastic lesion were significantly less in number than the neoplastic lesions--both benign and malignant, in both the HP section and FNAC smear. But the counts did not show significant difference in the two neoplastic lesions eg, fibroadenoma and infiltrating duct carcinoma-grade 2, in both the HP section and FNAC smear. The appearance of the dots, as felt by the observers, were more discriminating between the three lesions, eg, uniform small compact centrally placed in fibroadenosis; mostly uniform small compact but occasional large irregular in fibroadenoma and large irregular marginally located in infiltrating duct carcinoma. Counting was easier and the appearance of the dots more easily discernible in FNAC smear than the HP section as the smear was monolayer and the malignant cells were easily detected from macrophages and stromal cells. But the tissue fluid or secretions or blood when present in the smear gave the smear a dirty background which was disturbing to the observers. Thus this AgNOR technique, when applied in HP section or FNAC smear, appears cost ineffective, lengthy and tedious procedure; did not offer absolute histochemical discriminant for malignancy from benignancy. But the shape and size distribution and appearance of the dots showing much variability in FNAC smear than the HP section, might be of some help in the diagnosis of malignancy and discriminating from benignancy.

Study of myopathies by histological and histochemical methods with special reference to staining for desmin expression

An attempt was made to study the histological and histochemical changes as well as immunohistochemical changes in desmin expression occurring in four types of clinical myopathies e.g. Chronic ischaemic myopathy due to Buerger's disease (Group I), Carcinomatous myopathy (Group II), Metabolic myopathy (Group III) and Muscular dystrophy (Group IV). The number of cases studied were 16 cases, 15 cases, 4 cases and 5 cases respectively. The study revealed: (i) a combination of normal, degenerated, necrotic and regenerating fibres in different proportions in all the four groups having maximum number of degenerated fibres in Group I and Group IV, relatively more number of regenerating fibres in groups III and absence of necrotic fibres in Group I. (ii) Altered tinctorial property in most of the fibres indicating degenerated and regenerating fibres in all the groups with Masson's trichrome staining against inconstant staining with PTAH appear to be a good indicator for myopathy. (iii) The Desmin expression was week and irregular in most of the cases with most of the fibres probably due to reduction of desmin content probably indicating degenerated fibres, appear to be a good indicator for myopathy. (iv) Chronic ischaemic myopathy showed close resemblance with muscular dystrophy though no typical or distinct distinguishing feature could be identified in these four groups.

Cell mediated immune status in malignancy--pretherapy and post-therapy assessment

Twenty-eight cases of malignancies of different kinds were studied to assess T-cell activity and population before and after institution of therapy. Fifteen cases were diagnosed as non-metastasising squamous cell carcinoma of larynx, pharynx, laryngopharynx, hypopharynx and tonsils. Seven cases were non-metastasising infiltrating duct carcinoma of breast and 6 cases were non-Hodgkin's lymphoma (NHL). It was observed that 3 out of 15 cases (20%) of squamous cell carcinoma cases were Mantoux test (MT) negative with a T-cell population of less than 40%, 2 out of 7 cases (28.6%) of infiltrating duct carcinoma of breast were MT negative with a T-cell population of less than 40% and 3 out of 6 cases (50%) of NHL were MT negative with a T-cell population of less than 40%. The normal controls, consisting of apparently normal healthy adults, had a T-cell population of more than 40% and were all MT positive. The patients who showed a negative skin test and a T-cell population less than 40% were further subjected to assessment of T-cell population and activity after appropriate therapy, and clinical cure of the disease. It was observed that 2 out of 3 cases (66.66%) of squamous cell carcinomas, 2 out of 2 cases (100%) of adenocarcinomas and one out of 3 cases (33.33%) of NHL showed positive conversion with a T-cell population of more than 40%.

Dopamine D4 receptor-mediated inhibition of cyclic adenosine 3',5'-monophosphate production does not affect prolactin regulation

Under physiological conditions, PRL synthesis and secretion are predominantly under negative control by dopamine acting through dopamine D2 receptors present in the pituitary lactotroph cells. To investigate the role of D4 receptors in the regulation of PRL synthesis and secretion, we stably transfected the human D4 receptor complementary DNA into the somatomammotrophic cell line GH4C1. The pharmacological characteristics of D4 expressed in GH4C1 were in close agreement with previous D4 receptor studies in Chinese hamster ovary and COS-7 cells. In GH4C1 cells, activation of D4 receptor variants (D4.2, D4.4, and D4.7) resulted in a similar level of reduction in forskolin- and vasoactive intestinal peptide (VIP)-stimulated cAMP levels (33% and 50%, respectively). In addition, the forskolin-stimulated activity of cAMP response elements fused to the VIP promoter driving the lacZ reporter gene could be blocked by D4 activation. However, quinpirole treatment had a minimal effect on transiently expressed luciferase reporter gene driven by a proximal PRL promoter in one of the D4-expressing cell lines. In contrast, the dopamine D2short receptor expressing GH4ZR7 cells treated with quinpirole displayed a significant decrease (51.3 +/- 4.1%) in PRL promoter activity. VIP-stimulated PRL release was not affected by D4 receptor activation, whereas in GH4ZR7 cells, a significant decrease in VIP-stimulated PRL levels was observed. Neither PRL promoter activity nor PRL secretion levels were affected in control untransfected GH4C1 cells. From this study it appears that although the D4 receptor may be expressed in the anterior pituitary, it does not have a major effect on PRL promoter activity or PRL secretion in GH4C1 cells despite its ability to reduce cAMP production. This might explain why D4- over D2-preferring antipsychotics such as clozapine do not cause hyperprolactinemia.

Review the role of dopamine D4 receptors in schizophrenia and antipsychotic action

For the past 20 years the most enduring explanation for schizophrenia has been the dopamine hypothesis, which proposes that the dopaminergic system is overactive in this widespread disease. Classically, the D2 receptor formed the core of the dopamine hypothesis since there was considerable evidence for elevations of D2 receptor levels in the brains of schizophrenic patients, and because these receptors served as the primary target in mediating antipsychotic effects of most neuroleptics. However, the dopamine D4 receptor has recently received particular attention in this context. This is because the atypical antipsychotic, clozapine, which is effective in treating refractory schizophrenics without the side-effect profile of typical neuroleptics, displays a 10-fold higher affinity for D4 compared to D2 or D3 receptors. Furthermore, the concentration in plasma water of clinical doses ofclozapine correlates well with its in vitro binding affinity for D4, but not D2 or D3 receptors, suggesting that D4 is a potential target in mediating clozapine's antipsychotic effects. As well, marked elevations in the level of a D4-like site (not identical to the D4 receptor) has been seen in the striatum of postmortem schizophrenic brains, but not in control brains. Finally, the most interesting feature of the D4 receptor is perhaps the array of polymorphisms associated with it, creating structural diversity in this receptor that supercedes all other known catecholamine receptors. The existence of these D4 polymorphisms raises the possibility that structural variations of this receptor may be associated with an increased susceptibility to schizophrenia, or observed variations in individual response to clozapine treatment. However, several studies aimed at investigating these hypotheses could not establish a direct role of D4 in schizophrenia. Furthermore, no association was evident between the polymorphic forms of D4 and susceptibility to schizophrenia, or variable clozapine response. Nevertheless, investigations surrounding this receptor has been far from futile. The observations which support the idea that D4 might serve as a target for clozapine have significantly modified and extended our understanding of mechanisms underlying atypical antipsychotic treatment of schizophrenia, as well as the dopamine hypothesis for schizophrenia. Further characterization of this receptor may prove to be crucial in designing highly effective antipsychotic drugs with minimal contraindications.

Synaptic growth in the rod terminals of mice after partial photoreceptor cell loss: a three-dimensional ultrastructural study

Following partial loss of photoreceptor cells in the retina of mice afflicted by mutant genes, damaging light exposure, or old age, some of the remaining rod cells exhibited a process of growth in their synapses with the second order retinal neurons. This growth was recognized by the presence of multiple synaptic sites in some of the rod terminals in the outer plexiform layer. In this study, a comparative analysis of the microanatomical changes in the synaptic structures of the rod terminals in the retina of normal, rds homozygous and heterozygous mutant and light exposed albino mice was undertaken by using a computer-aided three-dimensional reconstruction. A rod terminal normally showed the presence of 1 synaptic complex consisting of a single synaptic ribbon located between 2 processes of horizontal cells and 2 bipolar cell dendrites. In a rod terminal showing an enlarged synaptic complex, 2 or 3 separate synaptic ribbons formed the centres of separate synaptic sites; each of the sites was characterized by the presence of 2 laterally placed horizontal cell processes and 2 bipolar cell dendrites. However, these processes from the multiple synaptic sites were observed to arise from the 2 horizontal and the 2 bipolar cell elements that were normally present in the rod terminal. Thus proliferation of synaptic sites in the rod terminals occurred through growth and sprouting from the processes of the second order neuronal components present within the terminals. The altered synaptic complexes in the variously affected groups were structurally comparable and appeared to have resulted from similar microanatomical changes. The increase in the frequency of rod terminals with multiple synaptic sites occurred as a sequel to increasing photoreceptor cell loss that was recorded at different age points in the different experimental groups. It is concluded that rod synapses in the adult mammalian retina possess structural plasticity that permits compensatory growth.

Cryptic initiation at the human D4 receptor reveals a functional role for the amino terminus

It was found that deletion of the initiator methionine of the D4 receptor results in the use of a cryptic initiation site in the putative first transmembrane region. We made use of this observation to investigate the role of the amino terminus of the D4 receptor. In vitro transcription and translation of D4.4 and a D4.4 deleted for the initiation codon (D4.4 delta NH2) resulted in the formation of protein products with a molecular mass of about 44 and 40.5 kDa, respectively. The molecular mass of 40.5 kDa suggests initiation in the putative first transmembrane region. Transient expression of various deletion mutants indicated that this receptor form can be expressed at up to 70% of the D4.4 control levels and provided support for the existence for an alternative translation initiation site in the first transmembrane domain, most likely at nucleotide +112 (the initiator methionine codon is designated as +1). The D4.4 delta NH2 mutant was stably expressed in CHO cells. Pharmacological analysis demonstrated no major differences in antagonist binding with the regular D4.4 receptor, while dopamine and quinpirole binding affinities were about 5-fold decreased. The half-maximal level (EC50) for blocking forskolin-stimulated cAMP levels by dopamine was about 10-fold lower as compared to D4.4. Furthermore, the functional efficacy is decreased by about 40%. These data suggest that the amino-terminal domain is not essential for proper expression, but does interfere with the functional activity of the receptor, possibly through stabilization of the active state. To our knowledge this is the first demonstration that the amino terminus of a dopamine receptor is involved in signal transduction.

Dopamine D4 receptor variant in Africans, D4valine194glycine, is insensitive to dopamine and clozapine: report of a homozygous individual

The D4Valine194Glycine receptor is a variant of the dopamine D4 receptor and is found in 12.5% of the Afro-Caribbean population. Glycine replaces valine at a position one amino acid away from a serine which is critical for the attachment of dopamine. To determine whether this mutation had an effect on the properties of the dopamine D4 receptor, we constructed this variant and tested the sensitivity of the expressed protein with various drugs. We found that the variant receptor was two orders of magnitude less sensitive to dopamine, clozapine and olanzapine. The variant receptor was insensitive to guanine nucleotide, indicating the absence of a high-affinity state or functional state. The one 15-year-old individual found homozygous for this variant also had sickle cell disease. The patient revealed an overall pattern of low weight and no axillary or pubic hair.

Fine needle aspiration cytology of ophthalmic lesions

Forty cases of ophthalmic lesions were subjected to fine needle aspiration cytology for pre-operative diagnosis which included retinoblastomas (5 cases), inflammatory and neoplastic lesions of the eyelid and lacrimal glands (29 cases) and extra-ocular orbital lesions (6 cases) inclusive of 3 cases of rhabdomyosarcomas. The lesions were distributed in both the eyes almost in equal proportions. Histological confirmation was obtained in 85% of cases; false positive in only one case with malignant neoplasm of the eyelid and false negative also in only one case with inflammatory pseudotumour which were, histologically, proved to be adenoma of tarsal gland and lymphocytic lymphoma respectively.