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Biomedical subjects

K Collins

Publications and source records attributed to K Collins.

At least 19 recordsLinked to original sources
PubMed1992

Expression and localization of villin, fimbrin, and myosin I in differentiating mouse F9 teratocarcinoma cells.

F9 embryonic carcinoma cells are a multipotent cell line which can be induced to differentiate into cells resembling the visceral endoderm, an extraembryonic absorptive epithelium characterized by apical microvilli. We have examined the role of villin, fimbrin, and myosin I, the major actin-binding proteins in the intestinal and visceral yolk sac microvilli, in the development of epithelial polarity and the assembly of the microvillus cytoskeleton in differentiating F9 cells. By immunoblot analysis villin was first detected at 4 days of differentiation. Confocal microscopy localized villin at Day 4 to the apical surface and by Day 6 to the basolateral surfaces as well. In comparison, fimbrin and myosin I were both present in undifferentiated F9 cells and became associated with the apical surface after villin during differentiation to visceral endoderm. The accumulation of villin, fimbrin, and myosin I at the apical surface in differentiating F9 cells correlated with the appearance of microvilli containing organized actin filament bundles. Two mouse villin cDNAs were isolated and characterized to examine villin expression during F9 differentiation. Mouse villin was encoded by two transcripts (3.8 and 3.4 kb) which differ in their 3'-noncoding region. Both villin mRNAs were first detected by Day 4 of differentiation and their appearance coincided with expression of the visceral endoderm marker alpha-fetoprotein. The pattern of expression and order of accumulation of villin, fimbrin, and myosin I in differentiating F9 cells are common to developing gut and yolk sac epithelium. This suggests that microvillus assembly is directed by a sequence of temporally and spatially regulated localizations of these actin-binding proteins.

Animals↗
PubMed1992

Changing trends in explanted intraocular lenses: a single center study.

Over a nine-year period, our practice removed 1,091 intraocular lenses. The most common type of lens requiring explantation was the closed-loop anterior chamber lens (58.6%). The Stableflex lens represented the largest percentage of all removed lens types (28.8%). The number of closed-loop anterior chamber lenses requiring removal peaked in 1988 and then gradually declined. All other lens styles have shown gradually increasing removal rates. Older style iris-fixated lenses and rigid anterior chamber lenses, which have not been implanted for several years, have increasing removal rates. Late breakage of fixational polypropylene sutures with pupil-supported iris-fixated lenses have occurred in five cases; the average time from implantation to suture breakage was 112 months.

Anterior Chamber↗
PubMed1992

Explantation of posterior chamber lenses.

A consecutive series of 119 explanted posterior chamber lenses is reviewed. Seventy (58.8%) were removed because of dislocation or improper fixation, 15 (12.6%) because of anisometropia, and 18 (15.1%) because of chronic inflammation. Sixty-two (52.1%) of these explantations probably occurred for reasons that can be avoided by changes in preoperative, operative, or postoperative techniques. The rate of posterior chamber lens explantations is quite low considering the large number of lenses implanted; with changing surgical techniques, we anticipate that the number of lenses requiring removal will decrease.

Aged↗
PubMed1992

Suppressor T-cell levels are unreliable indicators of the impaired immune response following thermal injury.

The presence of increased levels of suppressor T cells after thermal injury and their relevance remain controversial. It is unclear whether suppressor T cells are the cause or result of sepsis complicating thermal injury. Spleen cells from a standardized murine burn model and sham burn controls were studied and the relationship between the levels of suppressor cytotoxic T cells (CD8, Lyt-2+), helper T cells (CD4, L3T4+), response to concanavalin A (ConA) and to phytohemagglutinin (PHA) and interleukin-2 (IL-2) production was examined. Mortality following infection via cecal ligation and puncture (CLP) of matched controls was also studied. At day 7 postburn, mean ConA (70 +/- 12% of control) and PHA response (58% +/- 5.2% of controls) and IL-2 production (43% +/- 5.4%) were significantly less than sham burn values (100%; p less than 0.05). However, the mean percentage of cells staining with anti-Lyt-2 and anti-L3T4 (9.1 +/- 0.59 and 13.9 +/- 0.65) was similar to the mean percentage in sham burn animals (9.4 +/- 0.65 and 16.6 +/- 1.1). Furthermore, no significant differences were observed between burned mice and controls in helper (17.3% +/- 1.8% burn vs. 21.2% +/- 1.7% sham) or suppressor cell levels (7.8% +/- 1.2% burn vs. 8.6% +/- 0.7% sham) or helper-suppressor ratios on day 10 postburn. Mortality of 20 litter-matched controls subjected to CLP on day 10 postburn was 90%, which was significantly greater than the sham burn mortality of 20%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A cohort study of coagulase negative staphylococcal mastitis in selected dairy herds in Prince Edward Island.

The epidemiology and importance of coagulase negative staphylococcal (CNS) mastitis in Prince Edward Island had not been documented. To investigate this, a cohort of 84 cows at seven farms were quarter sampled eight times over a lactation, commencing with samples taken prior to drying off in the previous lactation. Thirteen species of CNS were isolated. The quarter prevalence of CNS mastitis varied from 4.8% to 6.4% in the first five months of lactation and increased to 14.2 to 16.6% in the last four months of lactation. The geometric mean somatic cell counts (SCC) for quarters infected with CNS and uninfected quarters were 90 x 10(3) and 64 x 10(3) respectively (difference significant at p > 0.005). The two month new infection risk of CNS was 9.0% while the two month elimination risk was 74.4%. Infection with CNS did not alter the risk of subsequent infection with Staphylococcus aureus. The results from this project support the classification of CNS as a minor pathogen in mastitis control programs.

Animals↗
PubMed1991

Hip fractures among the elderly: factors associated with in-hospital mortality.

Factors associated with mortality were examined for 27,370 hip fracture patients aged 65 years or older in Maryland hospitals, using discharge data for 1979-1988. Variables of interest included sociodemography, principal medical and injury diagnoses, E-code, year, disposition, and hospital. For both white males and white females, the hip fracture rate doubled with each 5-year increment in age. The overall proportion who died during hospitalization was 4.9% (n = 1,339). After multivariate adjustment, there remained a substantially increased risk of death for males. The relative odds (RO) of dying for males versus females were 1.6. Other factors associated with high relative odds of dying during hospitalization included the diagnosis of septicemia (RO = 12.3), pneumonia/influenza (RO = 4.9), and digestive system disorder (RO = 3.6). The RO of dying doubled in the presence of cardiac, neoplastic, or cerebrovascular disease. Patients with diagnoses of nervous system or mental disorder, hypertension, anemia, musculoskeletal system disease, or urinary tract infection were at decreased risk of dying. Results of the study suggest that the prevention or early diagnosis and treatment of serious infections in the elderly patient with a hip fracture remain an important challenge to clinicians.

Black or African American↗
PubMed1991

Myosin I: a new insight into the mechanism and cellular significance of actin-based motility.

From our work on brush border myosin I structure, activity, regulation, and function, we can begin to understand the significance of the diversification of myosin proteins. While myosin I and II proteins retain conserved elements of structure that may dictate their similar mechanisms of motility and actin-activated MgATPase activity, their unique structures may provide the basis for the distinct localization and regulation of the two myosin types. How does the tropomyosin-inhibited actin-binding site of myosin I differ from that of the tropomyosin-activated myosin II actin-binding site? What elements of the sites of interaction of the 110K-protein and calmodulin contribute to the conserved, light-chain dependent coupling of MgATPase activity to translocation and which confer the novel calcium regulation of dissociation in vitro? It seems that the evolutionary demand for diversification of cellular motility functions has been met, at least in the actin-based system, by the evolution of isoforms tailored in structure, activity, regulation, and localization to serve complementary needs.

Actins↗
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↗