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Biomedical subjects

L Marshall

Publications and source records attributed to L Marshall.

At least 91 records · Page 5Linked to original sources
PubMed1986

The interaction of melittin with calmodulin and its tryptic fragments.

Melittin has been found to interact with both the N- and C-terminal half-molecules of calmodulin, as well as the intact molecule, in the presence of Ca2+. The interaction results in a major change in the microenvironment of Trp-19, which is in a more nonpolar, solvent-shielded, and immobilized microenvironment in the complex. The properties of Tyr-99 and Tyr-138 of calmodulin are altered by complex formation. From measurements of the efficiencies of radiationless energy transfer from Trp-19 to the nitro derivatives of Tyr-99 and/or Tyr-138, it is concluded that Trp-19 is located in proximity to the C-terminal lobe of calmodulin in the complex.

Acrylamide↗
PubMed1986

Comparison of pure-tone audibility thresholds obtained with audiological and two-interval forced-choice procedures.

Audibility thresholds were measured at 500 and 4000 Hz with a standard clinical procedure and a two-interval, forced-choice (2IFC) adaptive procedure for 72 normal-hearing and hearing-impaired listeners, age 17 to 83. Psychometric functions were obtained for clinical, 2IFC, and Yes-No procedures. A measure of response bias was obtained from the Yes-No procedure. The 2IFC adaptive thresholds were 6.5 dB lower than audiological thresholds. The psychometric functions for the forced-choice procedures were generally shallower than those for the clinical procedure and were shifted to lower sound pressure levels. Response bias played a small role at best in accounting for the magnitude of the difference in threshold estimated by the adaptive and clinical procedures or for the differences among the psychometric functions.

Adolescent↗
PubMed1986

A new therapy for portal systemic encephalopathy.

This report describes a new therapeutic approach to the treatment of adults with portal systemic encephalopathy using sodium benzoate and sodium phenylacetate, two compounds that increase conjugated nitrogen excretion in the urine and that have been shown to be an effective treatment for children with congenital hyperammonemia. The study was a double-blind cross-over study in which each patient was his own control. All patients either improved their mental status (six of eight) or maintained a mental status comparable to that achieved with conventional therapy [lactulose or neomycin (two of eight)]. All decreased their blood ammonias on these medications and seven of eight improved their portal systemic encephalopathy index. It is suggested that these medications may be useful in the treatment of portal systemic encephalopathy.

Aged↗
PubMed1985

Sites of interaction of calmodulin with trifluoperazine and glucagon.

The combination of glucagon with calmodulin alters the microenvironment of Tyr-99, but not Tyr-138, and is blocked by the binding of trifluoperazine by calmodulin. Trp-25 of glucagon is probably involved in the zone of interaction, which may also overlap one or more strong binding sites for trifluoperazine. From energy transfer measurements, one strong binding site for trifluoperazine probably involves the N-terminal region of binding domain III. Energy transfer and other evidence suggest that the zone of contact with glucagon involves the N-terminal region of binding domain III.

Amino Acids↗
PubMed1985

Peritoneal fluid prostaglandins in various stages of the menstrual cycle: role in infertile patients with endometriosis.

Thirty-nine patients with pelvic endometriosis and 45 patients with no evidence of endometriosis were entered in this study. The mean age was 29 years for each group. The volume of peritoneal fluid showed an increase towards the end of the cycle in both groups. Although the volume was higher in the endometriosis group than the control group, the difference between them was not significant. The concentration of prostaglandins F2 alpha and E2 was higher in patients with endometriosis than in the control group. The difference was significant (P less than 0.05) during days 9-16 and 17-24 for both prostaglandins, and during days 1-8 for prostaglandin F 2 alpha only. The high concentration of prostaglandins in the periovulatory and early luteal phases of the cycle may have adverse effects on tubo-ovarian function in endometriosis patients. Prostaglandin studies in peritoneal fluid are of significance during days 9-24 of the cycle when the effect of regurgitated menstrual fluid in the early phase of days 1-8 may be avoided.

Ascitic Fluid↗
PubMed1984

The incidence of acute brain injury and serious impairment in a defined population.

Studies on the incidence and epidemiologic features of brain injury and the immediate medical outcomes are few, and published results have serious methodological inconsistencies which prohibit comparisons. This study provides incidence rates of brain injury among the residents of San Diego, California. Cases had clinical confirmation and onset of injury occurred during 1981. The 3358 cases identified represent a rate of 180/100,000 with males having a 2.2 times higher rate than females. Rates were highest for males aged 15-24 years and, for both genders, those over age 70. Forty-eight per cent of all cases were from transport-related causes, followed by falls (21%) and assaults (12%). Over 11% were dead-on-arrival, and 16% were classified as having moderate or severe brain damage on admission to a hospital. Age- and sex-specific incidence rates varied according to external cause of injury. For example, for most subcategories of motor vehicle crashes and for assaults, the incidence rate was highest among males aged 15-24, while for brain injuries from falls or firearms, highest incidence rates were observed in older age groups. Almost 7% of all cases discharged alive from an acute care hospital had significant neurologic sequelae. The impact of brain injury is discussed as a major unresolved public health problem.

Accidents, Traffic↗
PubMed1984

Cellular components in peritoneal fluid in infertile patients with and without endometriosis.

Cellular components in peritoneal fluid of infertile patients with and without endometriosis were evaluated in 102 patients with Wright's-Giemsa and Papanicolaou stains. The secretory activity of these cells was studied indirectly by assaying acid phosphatase, prostaglandin (PG) F2 alpha and PGE2 and complement components C3c and C4. The results showed that macrophages and lymphocytes were the dominant cells in peritoneal fluid of these patients. These cells were significantly increased in endometriosis patients, as compared with control subjects. In addition, peritoneal fluid acid phosphatase, PGF2 alpha and PGE2, and complement components C3c and C4 were significantly increased in patients with endometriosis. These cellular changes and their activation in peritoneal fluid may explain infertility associated with endometriosis.

Acid Phosphatase↗
PubMed1983

Reassessment of high-frequency air-bone gaps in older adults.

In order to assess whether a high-frequency air-bone gap characteristically exists in older adults, air- and bone-conduction thresholds were measured for 147 ears from subjects ranging in age from 19 to 87 years. Results indicated that there were no apparent age-related effects, as evidenced by the mean data, the SDs, and scatterplots showing individual data points. However, a small number of older adults did have high-frequency air-bone gaps. In order to gain a better understanding of underlying causes, additional subjects over 50 years of age with high-frequency air-bone gaps were recruited. Ear-canal collapse did not appear to be a predominant underlying factor. Cerumen obstruction, healed tympanic membrane perforations, and an apparent loosening in the middle-ear system all were observed in ears with high-frequency air-bone gaps.

Adult↗
PubMed1983

Real-time ultrasonography: a useful tool in the evaluation of the craniectomized, brain-injured patient.

Real-time ultrasonography is being used increasingly to establish the diagnosis of and serially assess intraventricular hemorrhage and hydrocephalus in neonates. The procedure requires an open fontanel because scatter from the bone occurs from direct application of the transducer to the skull and bone density precludes satisfactory imaging. With an adult, under circumstances where a bone flap is left out after intracranial procedures and the patient's clinical status is such that the patient cannot be transferred for computed tomographic scanning, real-time ultrasonography allows a safe, noninvasive, bedside demonstration of ventricular size, degree of shift of midline structures, and intraparenchymal and intraventricular lesions.

Adult↗
PubMed1983

Prolactin and thyroid-stimulating hormone responses to thyrotropin-releasing hormone in cases of hyperprolactinemia with normal and abnormal sella tomograms.

An intravenous bolus of 500 micrograms of thyrotropin-releasing hormone (TRH) was used to test prolactin and thyroid-stimulating hormone (TSH) responses in normoprolactinemic patients and in hyperprolactinemic patients with normal and abnormal sella turcica. The prolactin response showed a mean increment of 64.1 +/- 46.3 ng/ml in normoprolactinemic women. In patients with hyperprolactinemia, the mean increment was 14.1 +/- 22.4 ng/ml and 13.8 +/- 33.1 ng/ml for patients with normal and abnormal sella, respectively. The difference in the prolactin response between the normoprolactinemic patients and either group of hyperprolactinemic patients is significant (P less than 0.005). The mean baseline TSH in normoprolactinemic patients is significantly higher than in patients with hyperprolactinemia with normal and abnormal sella. The mean increment of TSH after TRH stimulation is significantly higher in normoprolactinemic patients than in either group of patients with hyperprolactinemia (P less than 0.005). These results suggest an inhibitory action of hypothalamic dopamine on the response of both prolactin and TSH to TRH in patients with hyperprolactinemia. The hypothalamic dopamine mechanism might also be the factor leading to suppression of baseline TSH levels in hyperprolactinemic patients. In addition, these results suggest that patients with hyperprolactinemia, with or without changes in the sella turcica, might have various degrees of the same pathology affecting the lactotropes.

Adult↗
PubMed1983

Modifications for the Starkey Hearing Science Laboratory.

Directions were given to modify the Starkey HSL for more efficient programming capabilities (Memory Address Modifier), subject response (Response Box), and feedback (Logic Control) functions. These modifications improved classroom demonstrations in that subject response, as in actual experiments, may be demonstrated, and more than one experiment can be programmed prior to class. These changes also improved the HSL potential for clinical and research applications.

Audiology↗
PubMed1982

Synergistic effect of Ca2+ and Mg2+ upon the interaction of phosphorylase kinase with glycogen.

Phosphorylase kinase (ATP: phosphorylase-b phosphotransferase, EC 2.7.1.38) forms molecular complexes with glycogen over a range of conditions. The extent of interaction at pH 7.0, 20 degrees C, is greatly enhanced in the simultaneous presence of Ca2+ and Mg2+. If either cation is absent, the extent of complex formation is substantially reduced. Significant changes in the physical properties of phosphorylase kinase are observed in the presence of Ca2+ plus Mg2+, suggesting that a conformational change may occur under these conditions.

Animals↗
PubMed1982

Management of ear-canal collapse.

Thresholds were measured at 250, 500, 1,000, 2,000, 3,000, 4,000, 6,000, and 8,000 Hz in 20 normal adult ears and in ten ears from adults with varying amounts of ear-canal collapse. To alleviate the attenuation caused by ear-canal collapse, ear-canal inserts, postauricular pads, or circumaural cushions (Telephonics 510-020) were used with earphones (TDH-49). The circumaural cushions provided the lowest thresholds for the listeners with ear-canal collapse. Although thresholds with the ear-canal inserts were comparable to those with the circumaural cushions for many of the listeners, the ear-canal inserts were not suitable for listeners with more severe ear-canal collapse because the insert was displaced when the supra-aural cushion was placed on the pinna. Thresholds with the postauricular pinna pads were higher than with the circumaural cushions for most individuals.

Adult↗