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Biomedical subjects

S Chakravarti

Publications and source records attributed to S Chakravarti.

14 recordsLinked to original sources
PubMed1990

The basement membrane glycoprotein entactin promotes cell attachment and binds calcium ions.

Mouse entactin derived from the extracellular matrix of M1536-B3 cells and from insect cells infected with a recombinant virus containing entactin sequences were shown to promote the attachment of mouse mammary tumor, human melanoma, and other cells. The cell attachment was inhibited by antibodies against mouse entactin but not by anti-fibronectin or anti-laminin antibodies. On a weight basis entactin was as effective as laminin in promoting the attachment of mouse mammary tumor cells. The attachment of cells to entactin was in part mediated by the integrin recognition RGD peptide sequence. This was demonstrated by the cell attachment properties of peptides derived from entactin which contained this sequence. Furthermore, the peptide RGDS could inhibit the attachment of mouse mammary tumor cells to entactin to approximately 60% of control. It is suggested that additional cell recognition sequences may be present in entactin. The direct binding of calcium ions to entactin was observed. It is probable that the binding sites reside in peptide sequences located toward the NH2 terminus region of entactin. This conclusion was supported by the demonstration that synthetic peptides, containing potential calcium binding sequences derived from entactin, bound calcium. In addition, a recombinant peptide containing the amino-terminal 330 amino acids of entactin also bound calcium ions. The significance of these properties of entactin is discussed.

Amino Acid Sequence↗
PubMed1990

Characterization of the basement membrane glycoprotein entactin synthesized in a baculovirus expression system.

A cDNA clone encoding the entire open reading frame of mouse entactin was constructed. This cDNA was inserted into Autographa californica multiple nuclear polyhedrosis virus and expressed in Spodoptera frugiperda, Sf9, insect cells. The recombinant entactin was produced in large quantities under the control of the polyhedrin promoter. Amino terminus sequence analysis indicated that the signal peptide in the preprotein was correctly cleaved. Polyclonal antibodies prepared against either the naturally occurring or recombinant entactin cross-reacted with both molecules in the native and denatured states. The recombinant molecule promoted cell attachment and exhibited a calcium- and temperature-dependent self-aggregation. These properties reflect those of the naturally occurring mouse molecule. Although entactin is an extracellular matrix component that is normally exocytosed, the vast majority of the molecules were localized inside the cell by immunoelectron microscopy where the molecules formed insoluble aggregates.

Animals↗
PubMed1979

Relation between plasma hormone profiles, symptoms, and response to oestrogen treatment in women approaching the menopause.

Out of a consecutive series of 300 patients seen at a menopause clinic, 82 complained of symptoms generally associated with the climacteric, although they were still menstruating. Vasomotor disturbances were absent in 42 of these patients (group 1) and present in 40 (group 2). Headaches, insomnia, and dyspareunia were the most common complaints among the women with vasomotor symptoms, whereas loss of libido and depression predominated in those without. Conjugated equine oestrogens (Premarin) 1.25 mg daily given for three weeks out of four relieved nearly all symptoms in group 2, but in group 1 the response was disappointing. The mean plasma oestradiol concentration in women with vasomotor symptoms was significantly lower than that observed during days 1-10 of the menstrual cycle, but plasma testosterone values were not significantly different from those observed in younger women. Plasma follicle-stimulating hormone (FSH) and luteinising hormone (LH) concentrations were similar to those seen after the menopause. Concentrations of these hormones in the women without vasomotor symptoms were similar to those in the younger, regularly menstruating women. After six months of oestrogen treatment patients in group 2 had a 2.1-fold increase in mean plasma oestradiol concentration, and plasma FSH and LH concentrations were reduced to 39% and 66% of their pretreatment values respectively; in group 1, however, no such pronounced changes occurred. High concentrations of FSH were present in patients with oestrogen-responsive symptoms, 15 U/1 being the diagnostic cut-off point. This measurement in the presence of characteristic symptoms therefore constitutes the best method of selecting patients for oestrogen-replacement therapy.

Adult↗
PubMed1977

Endocrine changes and symptomatology after oophorectomy in premenopausal women.

The symptomatic and endocrine changes following hysterectomy and bilateral oophorectomy have been studied in 100 patients, 1 to 31 years after surgery. The most frequent symptoms at the time of interview were depression (62 patients), insomnia (48 patients), loss of libido (46 patients) and dyspareunia (38 patients). Vasomotor symptoms were recorded in 28 patients. Although 94 patients claimed that hot flushes were the first symptomatic changes noticed, 60 had complete relief from these symptoms within 6 months of surgery; 34 patients had no symptoms and only 4 patients were taking oestrogen therapy at the time of interview. Plasma oestradiol and testosterone levels were 78 per cent and 27 per cent respectively below the mean values of day 1 to 10 of the menstrual cycle, similar to those found at comparable years after a normal menopause. The plasma FSH level was about 14 times and the plasma LH level about twice the respective preoperative value. Unlike after the normal menopause, these gonadotrophin levels did not show any decline with increasing age. There was no correlation between plasma hormone levels and the presence of vasomotor symptoms or depression.

Castration↗
PubMed1977

Effect of hormone replacement therapy on glucose tolerance in postmenopausal women.

Oral glucose tolerance tests were performed on 50 symptomatic postmenopausal women before and after three months of hormone replacement therapy. All patients were randomly allocated to one of five groups treated with various synthetic or so-called naturally occurring oestrogens. Therapy produced a significant deterioration of carbohydrate tolerance with sequential preparations containing 100 microgram of ethinyl oestradiol or graduated doses of mestranol up to 50 microgram. The conjugated equine oestrogen (1.25 mg daily) and oestrogen valerate (2 mg daily) treated groups did not show abnormal glucose tolerance. The decreased glucose tolerance may be due as much to dosage levels as to any metabolic characteristics of the various oestrogens prescribed.

Adult↗
PubMed1977

The climacteric.

Explore the source record for details and available documents.

Administration, Oral↗
PubMed1976

Hormonal profiles after the menopause.

The endocrinological changes of the climacteric have been defined by studying the concentrations of follicle-stimulating hormone (FSH), luteinising hormone (LH), androstenedione, testosterone, oestrone, and oestradiol in 60 normal postmenopausal women of different menopausal ages. The women were studied in six groups, according to the number of years since their menopause. One year after the menopause androstenedione, oestrone, and oestradiol concentrations were reduced to about 20% of the values recorded during the early proliferative phase of the menstrual cycle. At the same time the mean concentration of FSH had risen by a factor of 13-4 and that of LH by a factor of 3-0. Concentrations of both gonadotrophins reached a peak of 18-4 and 3-4 times the proliferative phase value respectively after two to three years, and then gradually declined in the next three decades to values that were 40-50% of these maximal levels. Testosterone concentrations remained mostly in the normal range for premenopausal women but were depressed to 60% of these levels two to five years after the menopause, and the mean androstenedione levels showed a significant increase in the same group of women. The concentrations of both oestrone and oestradiol remained consistently low for 10 years after the menopause, but oestradiol concentrations inexplicably increased in the last two decades, with levels at the lower end of normal range for reproductive women in six patients.

Age Factors↗
PubMed1975

Tubal pregnancy after sterilization.

Twelve cases of tubal pregnancy after sterilization operations are reported and the pathogenesis is discussed. Diagnosis is sometimes delayed because of the history of previous sterilization. It is paradoxical that the diagnosis of an intrauterine pregnancy after tubal sterilization is rarely in doubt yet the possibility of the fertilized ovum implanting in a tube known to have been damaged is sometimes overlooked. It is suggested that bilateral salpingectomy is the correct operative treatment for this condition.

Abdomen↗