SEARCH · Search PubMed

Results for “stroma”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1975

The role of pH in the regulation of carbon fixation in the chloroplast stroma. Studies on CO2 fixation in the light and dark.

1. The pH in the stroma and in the thylakoid space has been measured in a number of chloroplast preparations in the dark and in the light at 20 degrees C. Illumination causes a decrease of the pH in the thylakoid space by 1.5 and an increase of the pH in the stroma by almost 1 pH unit. 2. CO2 fixation is shown to be strongly dependent on the pH in the stroma. The pH optimum was 8.1, with almost zero activity below pH 7.3.Phosphoglycerate reduction, which is a partial reaction of CO2 fixation, shows very little pH dependency. 3. Low concentrations of the uncoupler m-chlorocarbonylcyanide phenylhydrazone (CCCP) inhibit CO2 fixation without affecting phosphoglycerate reduction. This inhibition of CO2 fixation appears to be caused by reversal of light induced alkalisation in the stroma by CCCP. 4. Methylamine has a very different effect compared to CCCP. Increasing concentrations of methylamine inhibit CO2 fixation and phosphoglycerate reduction to the same extent. The light induced alkalisation of the stroma appears not to be significantly inhibited by methylamine, but the protons in the thylakoid space are neutralized. The inhibition of CO2 fixation by higher concentrations of methylamine is explained by an inhibition of photophosphorylation. It appears that methylamine does not abolish proton transport. 5. It is shown that intact chloroplasts are able to fix CO2 in the dark, yielding 3-phosphoglycerate. This requires the addition of dihydroxyacetone phosphate as precursor of ribulosemonophosphate and also to supply ATP, and the addition of oxaloacetate for reoxidation of the NADPH in the stroma. 6. Dark CO2 fixation in the presence of dihydroxyacetone phosphate and oxaloacetate has the same pH dependency as CO2 fixation in the light. This demonstrates that CO2 fixation in the dark is not possible, unless the pH in the medium is artificially raised to pH 8.8.

Adenosine Triphosphate↗

PubMed1975

[Stroma formation in epithelial malignant tumors].

The mechanism of stroma-formation and rearrangement of the stroma was studied on 221 cases of cancer of the lung, stomach and mammary gland using histological, histochemical and electron-microscopy methods of investigation. It was established that multiplying epithelial elements of teh tumour induced proliferation of histiogenic and vascular fibroblasts, activating them. Active fibroblasts play a double role: they either produce fibres and interstitial matter of the tumorous stroma, or participate in desintegration of preceding and newly formed collagenous structures. The processes of stroma-formation comply with the conventional schemes of normal fibrillogenesis and rearrangement of the interstitial tissue. It was shown that fibroblasts of the tumour stroma was capable of phagocytosis of a mature collagen. It is supposed that in the course of the tumorous growth correlation between the parenchyma and stroma is maintained, the leading role being played by the epithelium.

Acid Phosphatase↗

PubMed1978

The mechanism of the control of carbon fixation by the pH in the chloroplast stroma. Studies with nitrite-mediated proton transfer across the envelope.

1. CO2 fixation of intact spinach chloroplasts is inhibited by nitrite in a pH-dependent mode. At pH 7.3 in the medium 1 mM NaNO2 and at pH 7.9 5 mM NaNO2 were required for 50% inhibition. 2. The addition of nitrite leads to an acidificiation in the stroma. It appears that nitrite renders the envelope permeable for protons resulting in a breakdown of the pH gradient between the external space and the stroma. 3. In view of earlier results on the pH sensitivity of C02 fixation it is concluded that this pH shift in the stroma is responsible for the observed inhibition of CO2 fixation by nitrite. 4. Octanoate and to some extent also high concentrations of bicarbonate and acetate have a similar effect as nitrite in inhibiting CO2 fixation through an acidification in the stroma. 5. The levels of the intermediates of the CO2 fixation cycle were measured. A strong rise of the levels of fructose- and sedoheptulose biphosphates and a concomitant decrease of the corresponding monophosphates was observed during inhibition of CO2 fixation. It appears that the enzymatic steps of the CO2 fixation cycle responsible for the overall inhibition of CO2 fixation caused by lowering of the H+ concentration in the stroma are fructose- and sedopheptulose bisphosphatase. These two enzymes have an important function in the light regulation of CO2 fixation.

Ammonium Chloride↗

PubMed1976

Light-dependent changes of the Mg2+ concentration in the stroma in relation to the Mg2+ dependency of CO2 fixation in intact chloroplasts.

(1) Light-dependent changes of the Mg2+ content of thylakoid membranes were measured at pH 8.0 and compared with earlier measurements at pH 6.6. In a NaCl and KCl medium, the light-dependent decrease in the Mg2+ content of the thylakoid membranes at pH 8.0 is found to be 23 nmol Mg2+ per mg chlorophyll, whereas in a sorbitol medium it is 83 nmol Mg2+ per mg chlorophyll. (2) A light dependent increase in the Mg2+ content of the stroma was detected wjem chloroplasts were subjected to osmotic shock, amounting to 26 nmol/mg chlorophyll. Furthermore, a rapid and reversible light-dependent efflux of Mg2+ has been observed in intact chloroplasts when the divalent cation ionophore A 23 187 was added, indicating a light-dependent transfer of about 60 nmol of Mg2+ per mg chlorophyll from the thylakoid membranes to the stroma. (3) CO2 fixation, but not phosphoglycerate reduction, could be completely inhibited when A 23 187 was added to intact chloroplasts in the absence of external Mg2+. If Mg2+ was then added to the medium, CO2 fixation was restored. Half of the maximal restoration was achieved with about 0.2 mM Mg2+, which is calculated to reflect a Mg2+ concentration in the stroma of 1.2 mM. The further addition of Ca2+ strongly inhibits CO2 fixation. (4) The results suggest that illumination of intact chloroplasts causes an increase in the Mg2+ concentration of 1-3 mM in the stroma. Compared to the total Mg2+ content of chloroplasts, this increase is very low, but it appears to be high enough to have a possible function in the light regulation of CO2 fixation.

Calcimycin↗

PubMed1975

Effects of solutes on the swelling pressure of the corneal stroma.

The chemical environment of bare, excised rabbit corneal stroma was varied to determine the effects of solutes on the swelling pressure. Measurements of changes in the thickness of the stroma are converted to hydration units which are in turn converted to a change in swelling pressure at the initial hydration. The order of effects on swelling pressure are compared to the Hofmeister series for polyelectrolyte gels and the results are analyzed in the context of a structural theory of the swelling pressure of corneal stroma proposed by Hart and Farrell and based on the gel properties of the stroma.

Animals↗

PubMed2026

Spatial Proteomics of the Normal Breast Collagen Stroma: Links to Density and Body Mass Index.

Collagen breast stroma can become a breast cancer risk factor, yet proteomic regulation of normal breast stroma remains poorly defined. This study evaluates the spatial regulation of the collagen proteome from normal breast tissue. Normal breast tissue sections from the Susan G. Komen tissue bank were used (n = 40), with data including genetic ancestry (n = 20 African ancestry; n = 20 European ancestry), body-mass-index (BMI), age, and mammogram density by the Breast Imaging Reporting and Data System (BI-RADS). 10-plex cell marker staining showed CD44 and COL1A1 markers modulated with BMI. Collagen fiber widths by second harmonic generation microscopy contrasted in BMI categories by genetic ancestry. Targeted extracellular matrix proteomics mass spectrometry imaging showed the collagen alpha-1(I) chain proteome was spatially heterogeneous across the normal breast microenvironment with site-specific post-translational modification of proline hydroxylation. Signatures computationally extracted from stroma-rich regions reported that 47 collagen peptides distinguished BI-RADS categories (area under the receiver operating curve >0.7; p-value >0.05). Multivariate modeling of collagen peptides, fiber metrics, and clinical features supported a strong positive association with BMI as a determinant of collagen alterations in the normal breast. This study provides a foundation for larger studies investigating the clinical value of spatial collagen proteome alterations in human breast.

Humans↗

PubMed1979

Characterization and biosynthesis of proteoglycans of corneal stroma from rhesus monkey.

The proteoglycans of the Rhesus monkey corneal stroma were characterized by analyzing both radiolabeled proteoglycans synthesized by corneas in organ culture and native corneal proteoglycans obtained by large scale preparations. The analyses indicate that the proteoglycans synthesized in organ culture were similar to, if not identical with, their counterparts in the stroma although they are synthesized in different prportions in vitro than they acumulate in vivo. The corneal stroma contains two proteoglycans. The chondroitin-dermatan sulfate proteoglycan consists of approximately 70% protein and has a Mr = approximately 100,000 to 150,000. It contains one chondroitin-dermatan sulfate side chain of Mr = approximately 55,000. The keratan sulfate proteoglycan consists of approximately 74% protein and has a Mr = approximately -40,000 to 70,000. It contains one or two keratan sulfate side chains with a Mr = approximately 7,000 each. Radiolabeling indicates that both proteoglycans contain glycoprotein-type oligosaccharides as part of their structure.

Amino Acids↗

PubMed1978

A method for preparing a viable corneal endothelial layer, completely denuded of overlying stroma.

A method for denuding Descemet's membrane by dissection of all overlying stroma, while preserving the corneal endothelial layer, was developed and evaluated. The technique consists in treating the stroma with trypsin and surgically removing the softened stromal layers. With an automated thickness-measuring technique, the endothelium-Descemet preparation was found to range from 23 to 42 micron in thickness. Endothelial cell morphology was normal under specular and light-transmission microscopic examinations. Under electron microscopy, the endothelial cells appeared intact, except for an increase in the number of intracellular vacuoles. Occasionally, small portions of an intercellular space were found to be mildly dilated, but the over-all integrity of the junctional complex was intact. In vitro, the viability of the preparation was comparable with that of a cornea with all layers intact. Endothelial resting membrane potentials, measured with intracellular microelectrodes, were found to be within the normal (33 +/- 2 mV) range. It is thus possible to obtain a viable endothelial layer, completely stripped of stroma.

Animals↗

PubMed1977

Weight, stroma to gland ratio, and mitotic activity of the human hyperplastic prostate.

The growth of the hyperplastic prostate of 12 patients was studied with an in vitro 3H-thymidine labeling method. The prostates were weighed and the stroma to gland ratio was analyzed. The mitotic activity of the glandular epithelium averaged 0.36 per cent (+/- 0.06 SE). No mitotic activity was found in the stromal tissue. There was a positive correlation between the weight of the prostate and the labeling Index of the glandular epithelium. Thus, the prostatic hyperplasia of these patients appeared to be purely glandular in form. The stroma to gland ratio was 70 to 80 per cent. It was found that most of the glandular follicles were mitotically quiescent, and that the mitotic activity was concentrated in a few of the follices. The results indicate that the growth of the hyperplastic prostate is caused both by the mitotic activity (hyperplasia) of the glandular epithelium and by the stromal hypertrophy. Thus, in vitro assay of the mitotic activity of the prostatic biopsies can be used for the estimation of the weight of the hyperplastic prostate. The possible role of the stroma in regulation of the mitotic activity of the glandular epithelium has been discussed.

Aged↗

PubMed2025

The impact of the live broadcast of Stromae's song L'enfer on social media publications, calls to the national helpline, and suicide attempt rates in France.

On January 9, 2022, Belgian pop singer Stromae performed his new hit "L'enfer" live on French TV. The song addresses his personal struggles with suicidal ideation. To evaluate the impact of Stromae's performance, we modeled the evolution of hospital admission rates for suicide attempts (SAs) in France, calls to the national suicide prevention helpline (3114), and Twitter publications mentioning the singer or the helpline. We employed the Gombay test to identify change points within each time series. We identified a significant increase in mean SA rates among women aged 20-24 years 6 days after the singer's performance. No similar effect was observed in the general population or other young age groups. The show was immediately followed by a peak in tweets referring to the singer, while Twitter activity related to the 3114 remained modest. We did not observe any increase in calls to the helpline. Celebrity testimonies about suicidal experiences can help alleviate stigma but should be accompanied by prevention messages to reduce the risk of contagion.

Humans↗

PubMed1979

Pseudocorpus luteum insufficiency: a local defect of progesterone action on endometrial stroma.

A 23-yr-old woman whose initial complaint was infertility demonstrated glandular stromal dissociation with failure of the endometrial stroma to undergo pseudodecidualization in repeated endometrial biopsies taken late in the luteal phase. As the clinical presentation was consistent with the inadequate corpus luteum syndrome, hormone measurements were performed. The endometrial biopsy was abnormal during cycles in which the serum pattern of progesterone, estradiol, FSH, and LH was normal. Exogenous progesterone did not correct the abnormality. The patient, by in vitro studies, has approximately one half the number of high affinity progesterone-binding sites in the cytosol fraction of her endometrium compared to preparations from two normal control subjects. Since her cytosol-binding protein was qualitatively identical to two control subjects, the incomplete maturation of her endometrial stroma may represent an absence or reduced number of stromal cytosol receptors and/or a resistance to specific hormone action in an individual target tissue.

Adult↗

PubMed1979

Chalones and stroma as possible growth-limiting factors in the rat ventral prostate.

In an attempt to determine the mechanism that limits the growth of the rat ventral prostate, atrophied ventral prostates from orchiectomized inbred rats were implanted into the ventral prostate of other inbred rats. Under the influence of endogenous or exogenous androgen the DNA content of the ventral prostates was increased above normal. This indicates that there is no soluble growth inhibitor diffused in the normal prostate in a concentration sufficient to block cell divisions of the epithelial cells. In other experiments pieces of plastic sponge were implanted into the rat ventral prostate. Orchiectomy and subsequent androgen treatment led to an increased cell number in the prostate. Histologic examination revealed an ingrowth of loose connective tissue and also of normal-looking prostatic tissue in the sponge. The results suggest that implantation of pieces of sponge induced increased growth of the fibromuscular stroma and a secondary proliferation of the epithelial cells. A growth control of the prostatic epithelial cells by the fibromuscular stroma is suggested.

Androgens↗

PubMed1975

[Morphogenesis of eleastotic transformation of breast cancer stroma (author's transl)].

Within the tissue proteins in stroma of breast cancer occured multifocal elastotic transformations. The transformations concern collagen bundles that are devoided of mucopolysaccharide substance. The fields of degenerated connective tissue take on the capacities to dye like elastic fibres. The authors suggest that the increase of elastotic material in stroma of breast cancer is bound with the collagen degradation that is caused by metabolites of cancer tissue. The phenomenon occured in all age groups and is not closely bound with the grade of histological malignancy of cancer.

Adult↗

PubMed1979

Influence of stroma-free hemoglobin solution on renal function in dogs.

In the presented series of experiments, stroma-free hemoglobin solution (SFHS) was used as a perfusate for extracorporeal perfusion of kidneys and for exchange transfusion. It was shown that SFHS was adequatly oxygenated both as perfusate during the extracorporal perfusion and in the lungs after the blood exchange. Furthermore, there was provided evidence that oxygen was being transported and released in the tissues. Histologic examination of the kidneys demonstrated hemoglobin casts in the glomerules. Most of them were seen after extracorporal perfusion of isolated kidneys, less frequently after perfusion in situ and few casts were present after exchange transfusion. The cause of these depositions may be small remnants of stroma in the preparation. Furthermore it is possible, that at the beginning of the extracorporal perfusion of the kidneys the urine pH was below 6 and then a hemoglobin casts formation could occur. There were essential no changes in urine pH in the course of blood exchange. In this group were only few casts present in the kidneys.

Animals↗

PubMed1977

Mixed germ cell-sex cord stroma tumor of the ovary associated with isosexual precocious puberty in a normal girl.

A case of mixed germ cell-sex cord stroma tumor occurring in a normal 8-year-old girl with 46XX karyotype is reported. The child presented with evidence of isosexual precocious puberty 3 years prior to the excision of the tumor. Although the tumor was known to be present at least 2 years prior to its excision and weighed more than 1 kg, there was no evidence of involvement of the adjacent organs or metastases at the time of excision. The contralateral ovary was normal. The endocrine activity abated following the excision of the tumor and the patient is well and free of disease 2 years after the operation. The literature concerning this entity is discussed and reviewed.

Adult↗

PubMed1978

Amyloid stroma in a tubular carcinoma of palatal salivary gland: a histochemical and ultrastructural study.

Amyloid as defined by positive Congo red green birefringence and STB red birefringence was observed in the stroma of a tubular carcinoma of minor salivary gland origin. The amyloid exhibited additional histochemical characteristics of immunamyloid, viz., positive DMAB-nitrate and DC-reactions and spontaneous autofluorescence. Electron microscopic studies of the epithelial tumor cells displayed large amounts of cytoplasmic microfilaments similar to those present in the extracellular amyloid masses. It is suggested that the amyloid is derived from spontaneous assembly or polymerization of cytoplasmic microfibrils of the dying tumor cells as has been proposed for the amyloid associated with the calcifying epithelial odontogenic tumor (CEOT).

Adenocarcinoma↗

PubMed1979

Atypical fibrous histiocytoma with myxoid stroma: a rare lesion arising from dura mater of the brain.

Intracranial fibrohistiocytic tumors are rare. This report is concerned with a 24-year-old white male who had an 8 month history of intermittent visual disturbance. Craniotomy revealed a large, completely intradural lesion on the floor of the left anterior cranial fossa without involvement of the leptomeninges or brain parenchyma. Gross and microscopic examination revealed that the fibrogenic portion of the tumor was composed of spindle shaped neoplastic cells arranged in storiform pattern, a hallmark of fibrohistiocytic tumor. In contrast to three previously reported cases of "fibrous xanthomas" involving the leptomeninges and superficial cortex of the brain, the present lesion is clearly originated from mesenchymal stem cell of the dura. The other distinct gross and microscopic feature was the presence of myxoid component which constituted about 40% of the entire lesion. The myxoid component had not been observed in previous 5 reported cases of intracranial fibrohistiocytic lesions. Since there was cellular pleomorphism with extremely rare mitosis, it was felt that the lesion be best designated as atypical fibrous histiocytoma with myxoid stroma.

Adult↗

PubMed2025

KDM3B Regulates Postradiation Fibrotic Responses in Prostate Stroma via N6-methyladenosine Modification of LOX.

PURPOSE: Genome-wide association studies have uncovered single-nucleotide polymorphisms (SNPs) linked to radiation therapy (RT)-induced toxicities in patients with prostate cancer. SNP rs17599026, located in intron 21 of the KDM3B gene, has been associated with late-onset urinary toxicity, with an increased frequency of urination observed 2 years post-RT compared with pretreatment conditions. This study aimed to explore the underlying mechanisms driving this association. METHODS AND MATERIALS: A clustered regularly interspaced short palindromic repeats-dead Cas9 prime editing system was used to mimic KDM3B genetic variants in prostate stromal cell lines. Murine models with wild-type and heterozygous Kdm3b genotypes were used to assess fibrosis following radiation. RNA immunoprecipitation, transcript stability assays, and protein analysis elucidated the role of N6-methyladenosine (m6A) modification in regulating lysyl oxidase (LOX) expression. α-ketoglutarate (α-KG) supplementation was tested for its effects on KDM3B protein stability, LOX expression, and fibrosis mitigation. RESULTS: The rs17599026 SNP reduced KDM3B protein expression via circular RNA and microRNA-mediated mechanisms, leading to decreased m6A modification and increased stability of LOX messenger RNA. Elevated LOX expression promoted collagen cross-linking and fibrosis in prostate stroma. α-KG supplementation restored KDM3B protein levels, reduced LOX expression, and mitigated fibrosis in vitro and in vivo. CONCLUSIONS: KDM3B genetic variations influence radiation-induced fibrosis through posttranscriptional regulation of LOX. Dietary α-KG supplementation may serve as a mechanism-based strategy to alleviate radiation toxicity in patients with prostate cancer, offering a potential therapeutic pathway to improve treatment outcomes.

Male↗