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R N Ghosh

Publications and source records attributed to R N Ghosh.

At least 19 recordsLinked to original sources
PubMed1997

Endocytosis.

Mammalian cells take up extracellular material by a variety of different mechanisms that are collectively termed endocytosis. Endocytic mechanisms serve many important cellular functions including the uptake of extracellular nutrients, regulation of cell-surface receptor expression, maintenance of cell polarity, and antigen presentation. Endocytic pathways are also utilized by viruses, toxins, and symbiotic microorganisms to gain entry into cells. One of the best-characterized endocytic mechanisms is receptor-mediated endocytosis via clathrin-coated pits. This type of endocytosis constitutes the major emphasis of this review, with a brief discussion of other endocytic mechanisms and their comparison with the receptor-mediated pathway. This review describes and evaluates critically current understanding of the mechanisms of entry of plasma membrane components such as the receptor-ligand complexes and membrane lipids as well as the extracellular fluid into cells. The intracellular sorting and trafficking of these molecules upon internalization are also described. The roles of endocytosis in physiological and pathological processes are discussed. These include maintenance of cell polarization, antigen presentation, glucose transport, atherosclerosis, Alzheimer's disease, and the endocytosis of toxins and viruses.

Animals↗
PubMed1997

Argyrophilic nucleolar organiser regions (AgNORs) in breast lesions.

Nucleolar organiser regions (NORs) demonstrated by argyrophilia of NOR-proteins are indicator of cellular proliferative activity. The NORs can be identified in the nuclei as brown or black dots with silver colloidal staining technique in formalin fixed paraffin sections and in cytology smears. Seventy-five cases including 45 tissue sections and 30 fine needle aspiration cytology (FNAC) smears of benign and malignant lesions of breast have been studied to evaluate the significance and practical application of AgNOR count per nucleus. Out of 45 tissue sections 15 belonged to fibrocystic disease, 10 fibro-adenomas and 20 carcinomas and of the 30 FNAC smears, 10 were fibrocystic disease, 8 fibro-adenomas and 12 carcinomas. In fibrocystic disease the mean AgNOR count was 1.60 (FNAC group-0.75, tissue section-1.61). In fibro-adenomas it was 1.61 (FNAC-1.63, tissue section-1.59). The mean count in carcinoma was 12.10 (FNAC-12.08, tissue section-12.10). The difference in AgNOR count in fibrocystic disease and fibro-adenoma was not significant, but that between benign breast lesion and carcinoma was significant. No difference was observed between FNAC and tissue section groups in benign or malignant lesions. The simple staining technique can be used as an additional criterion to differentiate the benign and malignant lesions of breast.

Biopsy, Needle↗
PubMed1996

Microglial cells internalize aggregates of the Alzheimer's disease amyloid beta-protein via a scavenger receptor.

Microglia are immune system cells associated with Alzheimer's disease plaques containing beta-amyloid (A beta). Murine microglia internalize microaggregates of fluorescently labeled or radioiodinated A beta peptide 1-42. Uptake was confirmed using aggregates of unlabeled A beta detected by immunofluorescence. Uptake of A beta was reduced by coincubation with excess acetyl-low density lipoprotein (Ac-LDL) or other scavenger receptor (SR) ligands, and Dil-labeled Ac-LDL uptake by microglia was blocked by excess A beta. CHO cells transfected with class A or B SRs showed significantly enhanced uptake of A beta. These results show that microglia express SRs that may play a significant role in the clearance of A beta plaques. Binding to SRs could activate inflammation responses that contribute to the pathology of Alzheimer's disease.

Alzheimer Disease↗
PubMed1996

Transferrin receptor containing the SDYQRL motif of TGN38 causes a reorganization of the recycling compartment but is not targeted to the TGN.

The SDYQRL motif of the cytoplasmic domain of TGN38 is involved in targeting TGN38 from endosomes to the TGN. To create a system for studying this pathway, we replaced the native transferrin receptor (TR) internalization motif (YTRF) with the SDYQRL TGN-targeting motif. The advantages of using TR as a reporter molecule include the ability to monitor trafficking, in both biochemical and microscopy experiments, using the natural ligand transferrin. When expressed in CHO cells, the SDYQRL-TR construct accumulated in juxtanuclear tubules and vesicles that are in the vicinity of the TGN. The SDYQRL-TR-containing structures, however, do not colocalize with TGN markers (e.g., NBD ceramide), and therefore the SDYQRL motif is not sufficient to target the TR to the TGN. The morphology of the SDYQRL-TR-containing juxtanuclear structures is different from the recycling compartment found in cells expressing the wild-type TR. In addition, the SDYQRL-TR-containing juxtanuclear compartment is more acidic than the recycling compartment in cells expressing the wild-type TR. The juxtanuclear compartment, however, is a bona fide recycling compartment since SDYQRL-TR was recycled back to the cell surface at a rate comparable to the wild-type TR, and sphingomyelin and cellubrevin, both of which label all compartments of the endocytic recycling pathway, colocalize with SDYQRL-TR in the juxtanuclear structures. These findings demonstrate that expression of the SDYQRL-TR construct alters the morphology and pH of endocytic recycling compartments rather than selectively affecting the intracellular trafficking pathway of the SDYQRL-TR construct. Therefore, the SDYQRL trafficking motif is not simply a molecular address that targets proteins to the TGN, but it can play an active role in determining the physical characteristics of endosomal compartments.

Acids↗
PubMed1995

Intracellular calcium levels correlate with speed and persistent forward motion in migrating neutrophils.

The relationship between cytosolic free calcium concentration ([Ca2+]i) and human neutrophil motility was studied by video microscopy. Neutrophils stimulated by a uniform concentration of an N-formylated peptide chemoattractant (f-Met-Leu-Phe) were tracked during chemokinetic migration on albumin, fibronectin, and vitronectin. [Ca2+]i buffering with quin2 resulted in significant decreases in mean speed on albumin. To further characterize the relationship between [Ca2+]i changes and motility we carried out a cross-correlation analysis of [Ca2+]i with several motility parameters. Cross-correlations between [Ca2+]i and each cell's speed, angle changes, turn strength, and persistent forward motion revealed (i) a positive correlation between [Ca2+]i and cell speed (p < 0.05), (ii) no significant correlation between turns and calcium spikes, and (iii) the occurrence of turns during periods of low speed. Significant negative correlations between [Ca2+]i and angle change were noted on the high adhesion substrates vitronectin and fibronectin but not on the low adhesion substrate albumin. These data imply that there is a general temporal relationship between [Ca2+]i, speed, and persistent motion. However, the correlations are not sufficiently strong to imply that changes in [Ca2+]i are required proximal signals for velocity changes.

Biophysical Phenomena↗
PubMed1995

Evidence for nonvectorial, retrograde transferrin trafficking in the early endosomes of HEp2 cells.

We have previously characterized the trafficking of transferrin (Tf) through HEp2 human carcinoma cells (Ghosh, R. N., D. L. Gelman, and F. R. Maxfield, 1994. J. Cell Sci. 107:2177-2189). Early endosomes in these cells are comprised of both sorting endosomes and recycling compartments, which are distinct separate compartments. Endocytosed Tf initially appears in punctate sorting endosomes that also contain recently endocytosed LDL. After short loading pulses, Tf rapidly sorts from LDL with first-order kinetics (t1/2 approximately 2.5 min), and it enters the recycling compartment before leaving the cell (t1/2 approximately 7 min). Here, we report a second, slower rate for Tf to leave sorting endosomes after HEp2 cells were labeled to steady state with fluorescein Tf instead of the brief pulse used previously. We determined this rate using digital image analysis to measure the Tf content of sorting endosomes that also contained LDL. With an 11-min chase, the Tf in sorting endosomes was 24% of steady-state value. This was in excess of the amount expected (5% of steady state) from the rate of Tf exit after short filling pulses. The excess could not be accounted for by reinternalization of recycled cell surface Tf, implying that either some Tf was retained in sorting endosomes, or that Tf was delivered back to the sorting endosomes from the recycling compartment. The former is unlikely since nearly all sorting endosomes contain detectable Tf after an 11-min chase, even though more than one third of the sorting endosomes were formed during the chase time. Furthermore, while observing living cells by confocal microscopy, we saw vesicle movements that appeared to be fluorescent Tf returning from recycling compartments to sorting endosomes. The slow rate of exit after steady-state labeling was similar to the Tf exit rate from the cell, suggesting an equilibration of Tf throughout the early endosomal system by this retrograde pathway. This retrograde traffic may be important for delivering molecules from the recycling compartment, which is a long-lived organelle, to sorting endosomes, which are transient.

Biological Transport↗
PubMed1995

Clinicopathological study of clinically undiagnosed cases of kala-azar with special reference to grading of parasites.

Clinicopathological study of 34 clinically undiagnosed cases of kala-azar has been undertaken with a view to establish the diagnosis and correlate the quantitative grading of Leishmania donovani in bone marrow/splenic aspirates with clinical features and duration of disease. The ages of the patients were between 5 and 45 years. The duration of illnesses ranged from 2-24 months with 47% having 2 months' duration. Splenomegaly was less than 7 cm in 70.5% cases. Anaemia, leucopenia and mild thrombocytopenia were present in all the cases. Aldehyde test was positive in 47% cases. Bone marrow aspiration revealed the parasites in 82.3% cases. L donovani was also observed in 66.6% cases of splenic aspiration including 6 cases where bone marrow failed to reveal the parasite. Grading of the parasites in bone marrow and splenic aspirates revealed majority of the cases (73.5%) were in 3+ and 4+ grades. No correlation between splenic size and duration of illness or parasite grading was detected. Neither any positive correlation between parasite grading and duration of illness was observed.

Adolescent↗
PubMed1994

Automated detection and tracking of individual and clustered cell surface low density lipoprotein receptor molecules.

We have developed a technique to detect, recognize, and track each individual low density lipoprotein receptor (LDL-R) molecule and small receptor clusters on the surface of human skin fibroblasts. Molecular recognition and high precision (30 nm) simultaneous automatic tracking of all of the individual receptors in the cell surface population utilize quantitative time-lapse low light level digital video fluorescence microscopy analyzed by purpose-designed algorithms executed on an image processing work station. The LDL-Rs are labeled with the biologically active, fluorescent LDL derivative dil-LDL. Individual LDL-Rs and unresolved small clusters are identified by measuring the fluorescence power radiated by the sub-resolution fluorescent spots in the image; identification of single particles is ascertained by four independent techniques. An automated tracking routine was developed to track simultaneously, and without user intervention, a multitude of fluorescent particles through a sequence of hundreds of time-lapse image frames. The limitations on tracking precision were found to depend on the signal-to-noise ratio of the tracked particle image and mechanical drift of the microscope system. We describe the methods involved in (i) time-lapse acquisition of the low-light level images, (ii) simultaneous automated tracking of the fluorescent diffraction limited punctate images, (iii) localizing particles with high precision and limitations, and (iv) detecting and identifying single and clustered LDL-Rs. These methods are generally applicable and provide a powerful tool to visualize and measure dynamics and interactions of individual integral membrane proteins on living cell surfaces.

Algorithms↗
PubMed1994

Quantification of low density lipoprotein and transferrin endocytic sorting HEp2 cells using confocal microscopy.

Numerous experiments on CHO cells have shown that endosomes are composed of separate vesicular and tubulovesicular compartments, such as the sorting endosome, the recycling compartment, and the late endosome. However, Hopkins et al. (Nature 346, 335-339, 1990) have reported that endosomes in HEp2 human carcinoma cells form an extensive tubular reticulum. To resolve their observations with previous results from CHO and other cells, we examined the sorting and intracellular transport of endocytosed macromolecules in HEp2 cells, using low density lipoprotein (LDL) and transferrin (Tf) to probe the lysosomally directed and recycling pathways, respectively. Fluorescent LDL and Tf were observed with laser scanning confocal microscopy to visualize simultaneously both probes' sorting and subsequent post-sorting behavior in HEp2 cells. Quantifying the 3-dimensional cellular distributions of fluorescent LDL and Tf, after a variety of pulsechase schemes, gave the ligands' trafficking rates. Initially, both ligands appear in the same punctate sorting endosomes, and fingers of Tf start extending from these sorting endosomes. Tf rapidly leaves dual-labeled sorting endosomes (t1/2 approximately 2.5 minutes) and enters a post-sorting recycling compartment from which it is recycled out of the cell (t1/2 approximately 7 minutes). We present both morphological and kinetic data supporting the existence of these two separate compartments along the recycling pathway in HEp2 cells. LDL remains in punctate sorting endosomes that eventually lose the ability to receive newly endocytosed LDL, and mature into late endosomes. The trafficking and sorting of Tf and LDL in HEp2 cells follow the same general scheme as in CHO cells, indicating that the tubular endosomes previously seen may be the tubular parts of the sorting endosomes and recycling compartments in these cells. We propose that the endosomes in the recycling pathway of HEp2 cells, as in CHO cells, are composed of short-lived sorting endosomes, accessible to both Tf and LDL, and long-lived post-sorting recycling compartments, which contain Tf and recycling receptors but not LDL.

Biological Transport↗
PubMed1994

Fine needle aspiration cytology of cervical lymphadenopathy with special reference to tuberculosis.

One hundred eighty cases of cervical lymphadenopathy have been studied by fine needle aspiration cytological examination followed by histopathologic examination of the excised lymph nodes. The diagnostic accuracy was 84.4% for tuberculous lymphadenitis by fine needle aspiration cytological examination. Observation of caseous necrosis (84.2%) and epithelioid cells (73.6%) were the most characteristic diagnostic features in the aspirated smears. Acid-fast bacilli were observed in 45.6% cases. Metastatic carcinoma also yielded a high diagnostic accuracy ie, 89%. Fine needle aspiration cytology has been found to be safe, quick, inexpensive with high diagnostic accuracy in cervical lymphadenopathy.

Adolescent↗
PubMed1993

Sclerema neonatorum--histopathologic study.

Histopathological study of 10 cases sclerema neonatorum showed subcutaneous fibrosis with lobulation in all the cases. 8 (80 percent) cases showed non-specific chronic inflammation of dermis and thinning of epidermis with atrophy of rete pegs and hypercollgenisation of dermis was evident in 70 percent cases. Fat necrosis with crystallisation of fat content was not a conspicuous feature.

Adipose Tissue↗
PubMed1993

Malignant lymphoma--a 15-year study report.

Analysis of incidence of different types of malignancies during 15 years showed occurrence of malignant lymphoma in 192 cases (4.1%). There were 82 cases (42.7%) of non-Hodgkin's lymphoma and 110 cases (57.3%) of Hodgkin's disease. Lymphocytic lymphoma, the major type observed among the non-Hodgkin's lymphoma with 58 cases (30.21%), showed a preponderance of well differentiated type (40 cases). Other cases in this group comprised mixed cellularity (2.08%), histiocytic (3.64%) and unclassified one (6.77%). Analysis of the Hodgkin's disease cases showed majority in it belonged to the mixed cellularity type (44.5%) followed by the lymphocytic predominant type (27.3%), lymphocytic depletion type (18.2%) and nodular sclerosing type (10%). The incidence of 14 cases of extranodal lymphomas was 7.3% among the lymphomas with maximum occurrence in the gastrointestinal tract (42.8%).

Adolescent↗
PubMed1992

Rare variant of acute promyelocytic leukaemia.

Acute promyelocytic leukaemia (APL) is a peculiar sub-type of acute myeloblastic leukaemia characterised by presence of atypical promyelocytes in bone marrow and peripheral blood and common occurrence of haemorrhagic episodes associated with disseminated intravascular coagulation. Two morphological forms of APL are recognised--typical hypergranular and microgranular or M3 variant. This microgranular form of APL is rare but has got some peculiar features and often can be diagnosed by peripheral blood smear examination alone without bone marrow examination. Three cases of microgranular form of APL observed during a period of 6 months are reported here.

Adult↗
PubMed1990

A case of pituitary apoplexy.

Pituitary apoplexy, an uncommon syndrome, presented in a 40-year-old Nigerian with severe impairment of vision and persistent headaches over a 4-month period. Surgical decompression successfully restored his vision. This case is presented with a review of the literature and discussed as the first case seen in this unit since it started 5 years ago.

Adult↗