Search PubMed⌕ Search

Biomedical subjects

G Hammond

Publications and source records attributed to G Hammond.

At least 37 records · Page 2Linked to original sources
PubMed1997

Hernia of the lung: a case report and review of literature.

Lung hernia is a protrusion of pulmonary tissue through an abnormal defect in the wall of the thoracic cavity. Though the hernias may be congenital, they are usually acquired following a penetrating injury and surgical intervention. Symptoms are usually vague and infrequent. Pain and discomfort may be present at the site of a chest swelling that increases with forced expiration and valsalva and is readily reducible. Diagnosis may be confirmed radiologically by an oblique chest roentgenogram or a computed tomographic scan. Lung hernias only occasionally require surgical repair. We report the case of a 38-year-old man with acquired lung hernia, through a thoracotomy scar, and presenting as chest pain. A review of the literature is presented.

Adult↗
PubMed1996

Functional significance of the early component of the human blink reflex.

The relationship between the size of the first electromyographic (EMG) component of the cutaneous blink reflex (R1) and onset of eyelid closure in human adults was determined in 4 experiments in which R1 size was varied by different means: change in stimulus intensity, paired stimulation, and warning. Two-phase lid movements were frequently seen, with an early small movement followed by a large rapid movement. All experiments showed that larger R1s were associated with shorter latencies of both movements. This covariation was general across participants and was independent of shifts in the excitability of the blink reflex pathways indexed by R1 latency, R2 latency, and R2 area (R2 is the more prolonged, later EMG component). The results indicate that R1 acts first to evoke an early lid movement and second to facilitate eyelid closure by the later R2 burst. Identification of this second behavioral function for R1 aids the interpretation of other findings and encourages its use as a model system.

Adolescent↗
PubMed1995

A set-theoretical requirement for nonphysical specificity in embodied evaluations of physical models of mind.

When confronting assertions that minds are physically driven, humans necessarily engage their capacity to imagine objects moving in ways unexhibited in visual examples of physical phenomena. This variety of mental imagery, however, being unspecifiable in a given human in point-to-point mappings on to physically constrained events (even in principle), therefore has a physically undefined necessity. Intervention in neurologic patients, therefore, if done according to criteria no more comprehensive than those delimiting physical paths from stimuli to responses, could not provide for that necessity. Provision for necessarily embodied mental imagery might be feasible if, in a given human, every progression through that human's mental space is permitted unique specification in mathematical hypotheses of brain.

Brain↗
PubMed1995

Hypothetical substrates of ideation compared in terms of mechanical and quasimechanical coherence of behavior.

Relationships between physiologic models and ideas in general require axioms for their expression. Axioms proposing that a given human's ideation is borne in trajectories of response owing their coherence to mechanical arrangement limit neurologic therapy to the arbitrary deflection of patients toward target behaviors. However, a patient's physiologic acts of describing environment, if coherent yet mechanically disjoint at their origins, could be proposed as ideationally-generated. Neurologic therapy could then be the aim to provide for their optimal use.

Brain↗
PubMed1995

Effect of maternal oxygen therapy on placental calcium transport in intrauterine growth retarded rats.

OBJECTIVE: We tested the hypothesis that continuous maternal oxygen (O2) therapy leads to an increase in fetal survival, improvement in fetal growth, and correction of decreased placental calcium (Ca) transport, in pregnant rats who underwent uterine artery ligation. STUDY DESIGN: We measured on Day 21 of pregnancy, the unidirectional maternofetal clearance of 45Ca (Kmf45Ca) and 51Cr-EDTA (Kmf51Cr-EDTA) across in-situ perfused placentas of rats randomized on Day 17 to a modified Wigglesworth (bilateral uterine artery ligation) procedure (group WW, n = 8), to modified Wigglesworth and supplemental maternal O2 treatment (FiO2 0.40) (group WWO2, n = 8), or to a sham operation (group Sh, n = 8). Kmf51Cr-EDTA provides a measure of placental "porosity" or passive permeability. RESULTS: Maternal O2 therapy did not improve fetal survival, fetal growth, or placental Ca transport. CONCLUSION AND SPECULATION: Bilateral uterine ligation in the pregnant rat leads to IUGR and decreased placental Ca transport which cannot be corrected by maternal O2 therapy.

Animals↗
PubMed1995

Evaluation and validation of a monoclonal immunofluorescent reagent for direct detection of Bordetella pertussis.

An outbreak of pertussis in Manitoba, Canada, provided an opportunity to evaluate the recently developed monoclonal antibody (MAb) BL-5 for the direct detection of Bordetella pertussis. The MAb recognizes a lipooligosaccharide epitope. A total of 1,507 consecutive nasopharyngeal swabs for culture and companion smears for direct fluorescent-antibody (DFA) detection were evaluated at Cadham Provincial Laboratory between September and November 1994. The cutoff for DFA positivity was four fluorescing organisms with morphology characteristic of B. pertussis. PCR analysis for B. pertussis DNA was performed on a subset of 100 smears by eluting material from the slides after DFA examination. In comparison with culture, the sensitivity, specificity, and positive and negative predictive values of BL-5 were 65.1% (41 of 63 samples), 99.6% (1,438 of 1,444 samples), 87.2% (41 of 47 samples), and 98.5% (1,438 of 1,460 samples), respectively. The sensitivity of culture compared with PCR was 45.5% (10 of 22 samples) for the subset of 100 specimens tested by both procedures. An expanded "gold standard" of positivity by culture or PCR for these 100 specimens resulted in DFA sensitivity, specificity, and positive and negative predictive values of 32.3, 97.1, 83.3, and 76.1%, respectively. The utility of MAb BL-5 for direct detection of B. pertussis in a clinical laboratory setting has been demonstrated by this investigation.

Adult↗
PubMed1994

Changes in spinal reflex excitability in a countermanded timed response task.

Subjects (N = 8) performed a timed response task in which they attempted to synchronize an impulsive foot-press response with the last in a series of four regularly spaced tones. In Experiment 1, the response was countermanded on one third of the trials (stop trials) by a stop signal that appeared at a predetermined delay after the third tone. No stop signal appeared on the remaining trials (go trials). All subjects showed a systematic transition from withholding the response on stop trials in which the stop signal appeared shortly after the third tone to executing the response on trials in which a single stop signal delay had been chosen so that a response would be made on about 50% of the stop trials. We elicited Hoffmann (H) reflexes from the soleus muscle on all trials to determine whether the reflexes were augmented on occasions on which a response was prepared but withheld. Mean H-reflex amplitudes on go trials and on stop trials on which the response was executed were similar and showed a marked augmentation beginning about 250 ms before response onset; mean H-reflex amplitudes on stop trials on which the response was withheld showed less pronounced augmentation. Inspection of individual H-reflex amplitudes revealed that on stop trials on which the response was withheld the reflexes could be augmented to the same extent as on trials on which the response was executed. This dissociation of H-reflex augmentation and response execution shows that H-reflex augmentation reflects a controlled response process. Ballistic response processes therefore must be limited to a brief duration.

Journal Article↗
PubMed1994

Epidemiology of infection due to Chlamydia trachomatis in Manitoba, Canada.

In a study of the epidemiology of Chlamydia trachomatis infection in Manitoba during 1981-1990, we retrospectively reviewed laboratory and clinical case notification records as well as hospital and health insurance data concerning pelvic inflammatory disease and ectopic pregnancy. After implementation of a control program in 1987, the annual incidence of chlamydial infection was highest among females aged 15-24 years (3,418 cases per 100,000 residents). Recurrent infection, which occurred in 13.4% of patients, was more common in women (P < .001), patients aged 15-24 years (P < .001), registered North American Indians (P < .001), and persons with concomitant gonorrhea (P < .001). Risk factors for dual (chlamydial and gonococcal) infection included male sex (P < .001) and young age (P < .001). Although the incidence of hospitalization and outpatient visits for pelvic inflammatory disease decreased (P < .001) from 1981 to 1990, the annual incidence of ectopic pregnancy increased from 10 to 16 cases per 1,000 reported pregnancies (P < .001). Control activities focusing on the primary prevention of C. trachomatis infection are presented. Strategies for improving secondary prevention (through case detection and treatment of lower genital infection) include the targeting of individuals with recurrent and multiple sexually transmitted diseases.

Adolescent↗
PubMed1993

Judgments of moving and intending to move in a timed-response task.

Subjects performed a timed-response task in which they attempted to synchronize a rapid flexion of the index finger of their preferred hand with the last of a train of four regularly spaced acoustic clicks. The task was used to stabilize the execution time of a simple voluntary response in order to facilitate psychophysical judgments about the subjects' perception of having responded and of having intended to respond. In the first experiment, male subjects (N = 6) adjusted the appearance time of a reference stimulus (a brief percutaneous pulse to the responding finger) until it appeared to be simultaneous with their perception of having made the response. All subjects adjusted the reference stimulus to appear after response onset during the latter half of the force impulse. This finding suggests that the perception of having responded is based on peripheral feedback from the response. In the second experiment, male subjects (N = 6) performed the same motor task, but adjusted the time of the reference stimulus so that it appeared to be simultaneous with their intention to respond. Two subjects were not able to do the task successfully; the remaining four subjects adjusted the reference stimulus to appear from 101 to 145 ms before response onset. This finding suggests that the intention to respond is perceptually separable from the response itself and occurs at a measurable time before response onset.

Adult↗
PubMed1993

A set-theoretical definition of the physical memories of stimuli.

Presumably, the memory of a stimulus exists as a difference in a system due to that stimulus, compared to what the system would have been had the stimulus never occurred. Thus every stimulus, to be remembered, must define with the system a set of phenomena perfectly divergent from those of other stimuli. Therefore there exist no subsets of physical phenomena common to memories of different stimuli, even those the experimenter classifies as equivalent. It is concluded that human awareness of groups of stimuli requires a dualistic explanation.

Brain↗
PubMed1993

Placental calcium transport during acute maternal hypermagnesemia in the rat.

OBJECTIVE: Our aim was to test the hypothesis that maternofetal placental calcium transfer rate decreases in experimentally induced acute maternal hypermagnesemia in the rat. STUDY DESIGN: We measured the unidirectional maternofetal clearance of calcium 45 and chromium 51-ethylenediaminetetraacetic acid across in situ perfused placentas of rats randomized to intravenous treatment with saline solution and magnesium sulfate (n = 5) or to saline solution only (n = 5) before placental perfusion. The maternofetal clearance of chromium 51-ethylenediaminetetraacetic acid provides a measure of placental "porosity" or passive permeability. RESULTS: The mean serum magnesium concentration increased to 5.3 +/- 0.6 mg/dl (2.18 +/- 0.25 mmol/L) in magnesium-infused rats, staying at 1.8 +/- 0.1 mg/dl (0.74 +/- 0.04 mmol/L) in control rats (p < 0.001). Neither the maternofetal clearance of calcium 45 nor that of chromium 51-ethylenediaminetetraacetic acid was affected by acute maternal hypermagnesemia. CONCLUSION: Within the range of hypermagnesemia studied, placental calcium transport remains unaffected.

Animals↗
PubMed1992

Effect of chronic maternal dietary magnesium deficiency on placental calcium transport.

Metabolisms of calcium (Ca) and magnesium (Mg) are closely interrelated in the intestine, bone, and kidney. Interaction of Ca and Mg at the placental level, however, is not well defined. The occurrence of decreased bone mineral content and hypocalcemia in infants of hypomagnesemic mothers led us to test the hypothesis that chronic dietary maternal Mg deficiency decreases placental Ca transport. On day 10 of gestation, 20 Sprague-Dawley rats were randomized to a Mg-deficient diet (3.3 mg/day, n = 10) or to a control diet (70 mg/day, n = 10). On day 20 of gestation (term = 22 days), intact placentas were perfused in situ through the umbilical artery and perfusate was collected through the umbilical vein. Calcium 45 (45Ca) and chromium 51-EDTA (51Cr-EDTA) (a diffusional marker for placental membrane integrity) were injected to the dam and steady state maternofetal clearance (Kmf45Ca, microliter/min/g placenta) of both isotopes were calculated. There was no difference in the clearance of 45Ca and 51Cr in both groups (55 +/- 10 vs 57 +/- 16 and 3.2 +/- 0.4 vs 3.6 +/- 0.4, respectively, mean +/- SEM). We conclude that, in the rat, placental Ca transfer is unaffected by chronic maternal dietary Mg deficiency. We speculate that Ca and Mg cross the placenta by independent mechanisms.

Animals↗
PubMed1991

Effects of maternally administered epidermal growth factor on placental permeability.

Epidermal growth factor is a well-studied modulator of epithelial membrane structure and function. Mammalian placentas are a rich source of epidermal growth factor receptors, but the role of epidermal growth factor in placental pathophysiologic conditions is unclear. To determine whether epidermal growth factor could affect mechanisms of placental transfer, we used an in situ rat placental perfusion model. Fourteen Sprague-Dawley rats that were 20 days pregnant were randomized to epidermal growth factor or placebo during placental transport experiments. We chose ethylenediaminetetraacetate tagged with chromium 51 as a marker of placental permeability. Epidermal growth factor treatment led to a dramatic increase of maternofetal clearances of chromium 51-ethylenediaminetetraacetate. We conclude that maternally administered epidermal growth factor has a potent action on placental permeability.

Animals↗
PubMed1989

Isolation and characterization of the cDNA for pulmonary surfactant-associated protein-B (SP-B) in the rabbit.

Pulmonary surfactant contains phospholipids including dipalmitoyl-phosphatidylcholine and three surfactant-associated proteins designated SP-A, SP-B and SP-C. A cDNA for rabbit SP-B has been isolated from a fetal (30 days gestation) rabbit lung cDNA library constructed in lambda gt11. The cDNA and deduced amino acid sequences show strong homology with the cDNAs and predicted 40 kDa proproteins for human and canine SP-B. Strong homology is also observed with the amino acid sequences directly determined for the mature 8 kDa bovine and porcine SP-B isolated from lung lavage. SP-B is remarkable for its high cysteine and proline content and for the hydrophobic nature of the organic solvent-soluble, mature protein. In vitro translation of sense but not antisense RNA transcribed from the cDNA led to the production of 40 kDa and 32 kDa proteins. These proteins were immunoprecipitated by an antibody raised against bovine SP-B. Northern blot analysis revealed the mRNA for rabbit SP-B appears in fetal rabbit lung late in gestation and falls slightly in the neonate.

Amino Acid Sequence↗
PubMed1989

Identification of proteins immunochemically related to human pregnancy-specific beta 1-glycoprotein in the rat placenta.

Human pregnancy-specific beta 1-glycoprotein (hPS beta G) consists of a set of glycoproteins present in placenta and maternal serum. This study characterized proteins in rat placenta that show immunological cross-reactivity with antisera to hPS beta G. Immunocytochemical studies using two independent preparations of anti-hPS beta G showed intense specific staining within basophilic cytotrophoblast cells of the basal zone of the gestation day 15 rat placenta. In contrast, basophilic cytotrophoblasts located in the labyrinth did not stain. Subsequent experiments used gel electrophoresis and immunoblot analysis to compare PS beta G in human placenta and serum with immunoreactive proteins in rat placenta and serum. A set of two or three proteins was detected in human villous tissue and pregnancy serum with apparent mol wt (Mr) ranging from 54,000-76,000. In contrast rat placenta showed a major immunoreactive protein with 120,000 Mr, while rat serum contained bands of 48,000 64,000 and 69,000 Mr. Explant cultures of rat basal zone tissue secreted two [35S]methionine-labeled proteins that were immunoreactive, a major 120,000 Mr species and a minor 76,000 Mr form, with pI values of 4.6-5.5; tunicamycin inhibited the secretion of both species. Thus, a 120,000 Mr glycoprotein appears to be the major tissue and secreted form of rat PS beta G analog in day 15 placenta. Finally, the cytochemical localization of PS beta G-like proteins in rat placenta showed a progressive gestational shift from giant trophoblast cells in the parietal yolk sac placenta on day 12 to the basal zone cytotrophoblast cells by day 15. Data indicate that the pregnant rat may provide an animal model for investigation of the biological function of PS beta G during late gestation.

Animals↗