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Biomedical subjects

A Harper

Publications and source records attributed to A Harper.

At least 55 records · Page 3Linked to original sources
PubMed1994

Nitric oxide in the rat vestibular system.

Nitric oxide is known to function as a neurotransmitter in the central nervous system. It is also known to be involved in the central nervous system excitatory amino acid neurotransmission cascade. Activation of excitatory amino acid receptors causes an influx of calcium, which activates nitric oxide synthase. The resulting increase in intracellular nitric oxide activates soluble guanylate cyclase, leading to a rise in cyclic guanosine monophosphate. The excitatory amino acids glutamate and aspartate are found in the vestibular system and have been postulated to function as vestibular system neurotransmitters. Although nitric oxide has been investigated as a neurotransmitter in other tissues, no published studies have examined the role of nitric oxide in the vestibular system. Neuronal NADPH-diaphorase has been characterized as a nitric oxide synthase. This enzyme catalyzes the conversion of L-arginine to L-citrulline, producing nitric oxide during the reaction. We used a histochemical stain characterized by Hope et al. (Proc Natl Acad Sci 1991;88:2811) as specific for neuronal nitric oxide synthase to localize the enzyme in the rat vestibular system. An immunocytochemical stain was used to examine rat inner ear tissue for the presence of the enzyme's end product, L-citrulline, thereby demonstrating nitric oxide synthase activity. Staining of vestibular ganglion sections showed nitric oxide synthase presence and activity in ganglion cells and nerve fibers. These results indicate the presence of active nitric oxide synthase in these tissues and suggest modulation of vestibular neurotransmission by nitric oxide.

Amino Acid Oxidoreductases↗
PubMed1993

Low-nutrient induction of abnormal chlamydial development: a novel component of chlamydial pathogenesis?

The intracellular development of chlamydiae in McCoy cells incubated in Eagle's minimal essential medium lacking all 13 amino acids was examined both by fluorescence and electron microscopy and by infectivity titration. Aberrant development occurred in almost all inclusions of strains of Chlamydia trachomatis and C. psittaci with the production of abnormal forms which differed in size, shape and internal structure from normal reticulate and elementary body forms. Detailed analysis of the response of C. trachomatis L2 strain 434 to graded reductions in amino acid level showed that infectivity was reduced and morphological abnormality increased as amino acid concentrations were lowered from 33 to 0% of amino acids present in minimal essential medium. Reversion of inclusions to normal and reappearance of infectious forms occurred on restoration of amino acids and further incubation. It is suggested that aberrant development may account for the presence in vivo of non-cultivable chlamydiae and that such development can arise via tryptophan deprivation mediated by local release of interferon gamma.

Amino Acids↗
PubMed1993

Foamy changes of placental cells in probable beta glucuronidase deficiency associated with hydrops fetalis.

Mucopolysaccharidosis type VII (MPS VII, beta glucuronidase deficiency) has been described in association with non-immune hydrops fetalis. Three consecutive pregnancies in an itinerant family, which resulted in stillbirths caused by non-immune hydrops are described. The parents were closely related and there was a strong family history of storage disorders. The main clue to the diagnosis, however, came from the presence of pronounced foamy cytoplasmic change in the villous Hofbauer cells of the placenta. This raised the possibility of an inherited metabolic storage disorder. The parents were subsequently shown to have beta glucuronidase activities in the heterozygous range in leucocytes and fibroblasts which suggested that the non-immune hydrops was caused by beta glucuronidase deficiency.

Female↗
PubMed1993

Managed care is in your future.

Though Texas has been slower than most other large states to move into managed care, it is gaining ground. According to the Texas Health Maintenance Organization Association, 1.2 million Texans were enrolled in HMO plans in January 1990. Three years later, 1.5 million had signed on--a 24 percent increase. State enrollment in other managed care plans, which aren't required to file reports with state regulatory agencies, was estimated to be 6.9 million (41 percent of Texans) in 1991, according to Blue Cross/Blue Shield. While these state enrollment figures are large, the most recent numbers available indicate that Texas hospitals have a long way to go. A 1991 AHA survey found that 259 Texas hospitals (47 percent of those surveyed) do not have contracts with HMOs or PPOs. With changes coming at break-neck speed, how can these hospitals position themselves to survive and prosper in the managed care world? This month, HealthTexas presents three examples of hospitals and health care systems that have successfully made the transition to managed care. Their stories illustrate three very different approaches--developing a network, direct contracting, and establishing a health plan. And, those who have led these ventures offer advice to help other hospitals make the transition a little easier.

Data Collection↗
PubMed1993

Primary team nursing: the 90s model.

The nursing shortage of the late 80s necessitated development of an alternative to primary nursing to meet patient needs. After assessing the strengths and limitations of functional nursing, team nursing and primary nursing, a team designed a new model which incorporated the best features of the three. After a pilot period, "primary team nursing" has proven effective and feedback from nurses has been positive.

Humans↗
PubMed1992

Long term predictive value of Doppler studies in high risk fetuses.

OBJECTIVE: To determine whether the predictive value of Doppler ultrasonography extends beyond the perinatal period. DESIGN: Descriptive follow-up study. SETTING: Specially designated paediatric clinic in Royal Maternity Hospital. SUBJECTS: 40 children who as high risk fetuses had had assessment of umbilical artery flow velocity waveforms. INTERVENTIONS: Parental history, physical examination, anthropometry, Denver developmental screening test. OUTCOME MEASURES: Weight, height, head circumference, neurological impairment, Denver development screening test RESULT: Abnormal waveforms were an accurate predictor of neonatal outcome, with significant differences in birthweight, gestational age, need for nursery admission, and frequency of intrauterine growth retardation between normal and abnormal waveform groups. However, abnormal Doppler studies were not predictive of long-term adverse sequelae. There were no significant differences in height, head circumference, proportion with neurological impairment, or results of Denver developmental screening test at a median age of five years. CONCLUSION: The predictive value of Doppler ultrasonography is less for long-term growth and neurodevelopment than for perinatal outcome in the high risk fetus.

Child↗
PubMed1991

Laser-assisted venous anastomosis: a comparison study.

A low-powered carbon dioxide laser was used to perform 25 vein grafts (50 anastomoses) on the femoral veins of Sprague-Dawley rats. The patency rate, clamp time, and bleeding time were compared with 50 conventional microvascular vein grafts (100 anastomoses). The patency of the laser-assisted anastomoses (LAVA) was 84 percent, while the conventional vein grafts yielded a 94 percent patency rate. The average clamp time and bleeding time for the LAVA were 47.2 min and 4.88 sec, respectively, while the conventional anastomoses required 57.6 min and had an average bleeding time of 9.44 sec. Histologically, both specimens healed at the same rate, but the laser-assisted anastomoses produced less inflammation and granulation tissue. These results suggest that the laser has potential as a tool for clinical application in microsurgery. In addition, the 94 percent patency rate achieved with the vein interposition graft would suggest that a decrease in the tension across the anastomosis can improve patency.

Anastomosis, Surgical↗
PubMed1991

Maternal and fetal haemodynamics in hypertensive pregnancies during maternal treatment with intravenous hydralazine or labetalol.

Intravenous treatment with 10 mg of hydralazine or 100 mg of labetalol was randomly allocated to 30 hypertensive pregnant women. Umbilical artery flow velocity waveforms were recorded using a pulsed Doppler duplex scanner (ATL Mk V) and umbilical artery pulsatility index (PI) and fetal heart rate (FHR) were derived from these recordings. Maternal blood pressure decreased significantly after both drugs. Maternal pulse rate increased after hydralazine but did not change significantly after labetalol. FHR did not change significantly after hydralazine but decreased after labetalol. PI decreased after hydralazine and increased after labetalol--most fetuses showed little change but a few in each group showed large changes in PI, as did two of five additional patients studied. We attributed the decrease in PI in some fetuses after hydralazine to vasodilation, and the increase in PI in some fetuses after labetalol to vasoconstriction in the fetoplacental circulation, suggesting that fetal beta-blockade may occur after maternal treatment with labetalol.

Adult↗
PubMed1991

Association of dry eye signs and symptoms with tear lactoferrin concentration.

Diagnoses of dry eye made with the Lactoplate Immunoassay Test (which assesses tear lactoferrin concentration) were compared to diagnoses based on dry eye symptoms, tear break-up times, and rose bengal staining. For a population of 49 subjects with normal and mild to moderate dry eyes, contingency tables showed that the lactoferrin-based diagnoses were not significantly related to the diagnoses made using any of the other factors. Lactoferrin concentrations were statistically correlated with symptom scores, but there was no significant correlation between lactoferrin concentrations and either tear break-up time or rose bengal staining. These results suggest that: 1) the dry eye problems in the subject population may not have been associated with lacrimal gland dysfunction (which the Lactoplate assesses); 2) Lactoplate tests are not sensitive enough to allow accurate diagnoses for the population of mild to moderate dry eye subjects used; 3) signs and symptoms associated with dry eyes occur before lactoferrin changes are manifest so lactoferrin changes had not yet appeared in the subjects; or 4) in mild to moderate dry eye subjects, lactoferrin changes occur only in reflexive tears and not in the basal tears that were tested in this study. In summary, measurement of tear lactoferrin concentration alone has not been shown to be a sufficiently sensitive and specific test for the diagnosis of mild to moderately dry eye as defined by more common clinical techniques.

Adult↗
PubMed1990

Evidence for a third structural class of beta-1,3-glucanase in tobacco.

Glucan endo-1,3-beta-glucosidases (beta-1,3-glucanases) have been implicated in several developmental processes and they may also play a direct role in the plant's defense against fungal pathogens. In an effort to characterize the glucanase gene family, complementary DNA clones encoding an acidic form of beta-1,3-glucanase have been isolated from tobacco. The cDNA was expressed in E. coli and shown to encode a beta-1,3-glucanase activity. The protein sequence encoded by the cDNA was found to match the partial protein sequence of PR-35, a previously characterized beta-1,3-glucanase. The protein encoded by the cDNA was purified from the extracellular fluid of TMV-infected tobacco leaves and found by immunological methods to correspond to glucanase PR-Q'. From a detailed analysis of the cDNA it is clear that this glucanase represents a third structural class of enzyme which differs substantially from both the basic, vacuolar glucanase and the acidic, extracellular forms (PR-2, PR-N and PR-O). It has previously been demonstrated that the basic form of beta-1,3-glucanase is synthesized as a pre-pro-enzyme and upon maturation the 21 amino acid signal peptide and a 22 amino acid carboxy-terminal peptide are removed. This processing event has been proposed to be involved with the vacuolar localization of the enzyme. By comparing the deduced protein structure of PR-Q' to that of the basic form it is evident that this extracellular enzyme is missing the carboxy-terminal 22 amino acids. The role of a conserved phenylalanine-glycine dipeptide in the processing of glucanases and other pathogenesis-related proteins from tobacco is discussed.

Amino Acid Sequence↗
PubMed1990

Isolation of complementary DNA clones encoding pathogenesis-related proteins P and Q, two acidic chitinases from tobacco.

Complementary DNA clones encoding two isoforms of the acidic endochitinase (chitinase, EC 3.2.1.14) from tobacco were isolated. Comparison of amino acid sequences deduced from the cDNA clones and the sequence of peptides derived from purified proteins show that these clones encode the pathogenesis-related proteins PR-P and PR-Q. The cDNA inserts were not homologous to either the bacterial form of chitinase or the form from cucumber but shared significant homology to the basic form of chitinase from tobacco and bean. The acidic isoforms of tobacco chitinase did not contain the amino-terminal, cysteine-rich "hevein" domain found in the basic isoforms, indicating that this domain, which binds chitin, is not essential for chitinolytic activity. The accumulation of mRNA for the pathogenesis-related proteins PR-1, PR-R, PR-P, and PR-Q in Xanthi.nc tobacco leaves following infection with tobacco mosaic virus was measured by primer extension. The results indicate that the induction of these proteins during the local necrotic lesion response to the virus is coordinated at the mRNA level.

Amino Acid Sequence↗
PubMed1990

Continuous wave Doppler flow velocity waveforms from the umbilical artery in normal pregnancy.

The objective was to establish a normal reference range of the indices of umbilical artery waveforms using continuous wave doppler ultrasound. A prospective longitudinal study was made of 85 uncomplicated singleton pregnancies between 16 and 40 weeks gestation (783 recordings). Pulsatility Index (P.I.), Resistance Index (R.I.) and A/B ratio were measured at each visit. The mothers all delivered normal healthy infants weighing more than the 10th centile for gestational age. All three indices have a positively skewed frequency distribution, a factor not generally appreciated until recently and the ranges are therefore described using non-parametric statistics. Placental resistance decreases as term approaches, the 50% PI at 16 weeks was 2.06, at 32 weeks was 1.08 and at 40 weeks was 0.85. The results show a comprehensive reference of normal values and provides a sound basis for the further study of abnormal pregnancy. It represents the largest published study of its type using continuous wave Doppler.

Adolescent↗
PubMed1989

Effects of neurite-promoting factors on rat sciatic nerve regeneration.

Neurite promoting factors (NPF), fibroblast growth factor, and laminin were instilled inside autologous venous nerve conduits (AVNC) interposed across a 1 cm gap in the rat sciatic nerve. Axonal regeneration was measured electrophysiologically and histologically and was compared to control AVNC and autologous nerve grafts (ANG) in 45 rats. By 1 month, the AVNC group with NPF recovered an average nerve conduction velocity twice that of the ANG group (24 m/sec vs. 12 m/sec). The gastrocnemius muscle action potential of NPF grafts was twice that of the control AVNC and was similar to the ANG (1.63 mV vs. 0.87 mV). In subsequent months, the advantage of NPF disappeared; these grafts were grossly reduced to fibrous bands. Histological examination of these grafts at 5 months revealed a florid intraluminal fibrovascular proliferation, which appeared to be "choking off" the regenerating axons. It is suggested that more refined mixtures of NPF should be instilled inside AVNC so that the improved axonal regeneration is maintained while the late inhibitory fibrosis is avoided.

Animals↗
PubMed1987

A training model for the stereomicroscopic evaluation of flap survival.

The stereomicroscopic appearance of the vasculature and circulation of groin flaps, with their epigastric pedicles divided at various time intervals, is an early diagnostic indication of flap viability. A simple and comprehensive training model, with characteristic vascular and flow changes within a single flap, is provided in rats, with pedicles transected at three to four days after the flap is raised.

Animals↗