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Biomedical subjects

K Collins

Publications and source records attributed to K Collins.

At least 91 records · Page 5Linked to original sources
PubMed1991

Differential regulation of vertebrate myosins I and II.

Cell motility events require movement of the cytoskeleton. Actin-based movement is catalyzed by the mechanoenzyme myosin, which translocates toward the barbed end of actin filaments in an ATP-dependent fashion. There are two subclasses of myosin with different structures and functions: conventional filamentous myosin (myosin II) and monomeric myosin I. Vertebrate non-muscle myosins I and II function as similar actin motors in vitro, catalyzing virtually identical actin-activated MgATP hydrolysis and motility. The functional diversification of these two enzymes results from their differential regulation. Calcium and tropomyosin, which activate the MgATP hydrolysis and motility of vertebrate non-skeletal muscle myosin II proteins, inhibit vertebrate (brush border) myosin I. The activities and regulation of brush border myosin I provide insight into conserved and unique features of the myosin mechanoenzymes and suggest how the functions of myosins I and II are divided in vertebrate cells. Brush border myosin I as an enzyme also contributes to our understanding of the molecular mechanism of motility.

Animals↗
PubMed1991

Sexual activity and contraceptive use among low-income urban black adolescent females.

A modified form of Nathanson and Becker's (1983) Health Belief Model Questionnaire and other measures designed to assess cognitive processing were administered to low-income black adolescent female clients of an inner-city comprehensive health care clinic. The purpose of the study was to explore determinants of sexual activity and contraceptive use. Subjects were classified as not sexually active (n = 50), sexually active/noncontracepting (n = 20), or sexually active/contracepting (n = 72). Not sexually active subjects tended to be younger, more career motivated, to have a father at home, to be more influenced by family values, and to have more conservative attitudes regarding adolescent sexuality than did sexually active subjects. Sexually active/noncontracepting subjects tended to report fewer benefits and more barriers to the use of contraception. Level of cognitive processing did not differ among the three groups, but was at a lower-than-expected level for age. Finally, inconsistent contraceptive use was common to both sexually active groups.

Adolescent↗
PubMed1990

Calmodulin dissociation regulates brush border myosin I (110-kD-calmodulin) mechanochemical activity in vitro.

110-kD-calmodulin, when immobilized on nitrocellulose-coated coverslips, translocates actin filaments at a maximal rate of 0.07-0.1 micron/s at 37 degrees C. Actin activates MgATPase activity greater than 40-fold, with a Km of 40 microM and Vmax of 0.86 s-1 (323 nmol/min/mg). The rate of motility mediated by 110-kD-calmodulin is dependent on temperature and concentration of ATP, but independent of time, actin filament length, amount of enzyme, or ionic strength. Tropomyosin inhibits actin binding by 110-kD-calmodulin in MgATP and inhibits motility. Micromolar calcium slightly increases the rate of motility and increases the actin-activated MgATP hydrolysis of the intact complex. In 0.1 mM or higher calcium, motility ceases and actin-dependent MgATPase activity remains at a low rate not activated by increasing actin concentration. Correlated with these inhibitions of activity, a subset of calmodulin is dissociated from the complex. To determine if calmodulin loss is the cause of calcium inhibition, we assayed the ability of calmodulin to rescue the calcium-inactivated enzyme. Readdition of calmodulin to the nitrocellulose-bound, calcium-inactivated enzyme completely restores motility. Addition of calmodulin also restores actin activation to MgATPase activity in high calcium, but does not affect the activity of the enzyme in EGTA. These results demonstrate that in vitro 110-kD-calmodulin functions as a calcium-sensitive mechanoenzyme, a vertebrate myosin I. The properties of this enzyme suggest that despite unique structure and regulation, myosins I and II share a molecular mechanism of motility.

Actins↗
PubMed1989

Familial torsion of the spermatic cord.

Familial spermatic cord torsion is rare. We present the fifth recorded family with this condition. Due to awareness of the condition and its consequences on the part of the family there was minimal delay in presentation and early testicular salvage occurred in all 4 patients.

Adolescent↗
PubMed1989

Twenty-five years of renal trauma at a teaching hospital.

In a study of 535 patients with renal trauma admitted to the Medical College of Virginia Hospitals from 1962 to 1988, the authors found indications of a decrease in the rate of total nephrectomy in patients with blunt trauma, due in part to advances in diagnostic technology. In the cases of gunshot wounds, however, a persistently high rate of nephrectomy prevailed, reflecting, the authors believe, the proliferation of increasingly lethal weaponry.

Humans↗
PubMed1988

Diffuse positive waves: case report.

Positive sharp waves occur in a variety of neurogenic, myogenic, and metabolic disorders. Although not synonymous with denervation, their presence is usually associated with some type of pathology. The authors found only one reported series of patients who had diffuse insertional positive waves but no demonstrable underlying disease. There were no follow-up reports and no other cases have been described. A patient is reported with diffuse insertional positive waves. He has been followed for over three years, remaining clinically normal. No electrolyte or metabolic abnormalities have been found. Two of the patient's four children showed normal results to limited EMG screening. This syndrome may represent an intrinsic defect in the muscle fiber cell membrane which makes it inherently unstable. It may also represent a form of myotonia; however, no evidence of that disease was found in this patient. This defect, which can only be detected by needle EMG, has so far not been associated with any neuromuscular deficit.

Electromyography↗
PubMed1987

Hormone ban.

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Animal Husbandry↗
PubMed1986

Leigh's disease.

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Brain Diseases, Metabolic↗
PubMed1985

Customized adjustable orthoses: their use in spasticity.

Spastic contractures are a common problem which frequently requires the use of splinting or casting. Customized adjustable orthoses can reduce contractures without the problems often associated with these procedures. These devices reduced contractures in a head-injured patient's severely spastic wrist and ankles. As a wrist contracture decreased, the patient increasingly used her arm and hand for feeding, grooming, and leisure activities. The plastic orthoses, molded to the individual limb, incorporate Klenzak or Lehrman fracture brace joints. Custom fit positions spastic limbs and promotes improved range of motion. Small brace joint adjustments are done at intervals to promote slow stretch of spastic limbs; since the device remains on during the adjustment, there is no loss of range of motion. The device may be removed for skin monitoring. The patient maintains joint range, as the orthosis becomes a permanent part of the home program. High cost of the device is potentially offset by the advantages of decreased skin morbidity, reduced therapist time in making adjustment, and maintenance of gains in range of motion. Such orthoses also have been used for elbow contractures.

Adult↗
PubMed1984

Birth of rhesus monkey infant after in vitro fertilization and nonsurgical embryo transfer.

The birth of a rhesus monkey resulting from in vitro fertilization is reported. Oocytes recovered at laparoscopy from five gonadotropin-stimulated donors were inseminated in vitro with sperm preincubated with caffeine and dibutyryl cyclic AMP. After insemination, oocytes were cultured for 33-46 hr. Twenty-two embryos were transferred nonsurgically into 11 recipient females. One recipient showed signs of implantation but did not carry to term. A second female became pregnant after receiving one 4-cell and one 6-cell embryo fertilized in vitro. The subsequent course of early pregnancy and embryonic and fetal development were characteristic of normal singleton pregnancies. A healthy term male infant was delivered by Cesarean section 176 days after fertilization. This birth has validated our procedures for in vitro fertilization of rhesus monkey gametes and provides an experimental model for studies of early embryonic development in primates.

Animals↗
PubMed1984

Leave-takings and reunions of infants, toddlers, preschoolers, and their parents.

The leave-taking and reunion behaviors of infants, toddlers, preschoolers, and their parents were observed as the children were "dropped off" and "picked up" at their nursery school each day. On arrival at their classroom, infants and toddlers related primarily to their parents, whereas preschoolers related to their teachers. Girls more frequently engaged in interaction with their teachers, and boys more frequently approached the children's play activities. Distress behaviors during the parents' departures were most frequently shown by toddlers, and the toddlers' parents hovered about them and " sneaked out of the room" more frequently. Children dropped off by mothers versus fathers showed more attention-getting behavior and crying, and mothers versus fathers engaged in more "distracting-the-child" behaviors and showed a longer latency to leave the classroom. During the second semester of observations parents and children spent less time relating to each other during leave-taking, children protested the departures less frequently, and the parents left the classroom more quickly. Regression analyses on distress behaviors during leave- takings and ambivalent behavior during reunions suggested that parent behaviors such as verbal explanation, distracting the child, latency to leave, and " sneaking out of the room" were correlated with children's distress and leave-taking distress was related to ambivalent behavior at reunion.

Attitude↗
PubMed1983

Fatal infection in mice after injection of immunosuppressive serum fractions from surgical patients.

Following surgical or accidental trauma many patients show suppression of cellular immunity. In this investigation sera from severely burned patients and patients undergoing aortic aneurysm repair were studied. Sera shown to suppress phytohaemagglutinin-induced blastogenesis of normal human lymphocytes were fractionated using ion exchange and G25 Sephadex chromatography. Suppressive activity was largely confined to a low molecular weight (LMW) fraction and was dose dependent. LMW fractions of normal sera had no significant suppressive activity. The purpose of this study was to test the causal relationship between immunosuppressive serum and decreased resistance to bacterial infection. Listeria monocytogenes infected mice were used as an in vivo model to test suppression of cellular immunity. Injection of LMW fractions of suppressive sera significantly increased mortality in these mice, but had no effect on non-infected mice. There was good correlation between the in vitro and in vivo effects of the suppressive fractions. These results suggest that a circulating factor in the serum of injured patients suppresses cellular immunity and may be responsible for impaired resistance to infection.

Adult↗