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Biomedical subjects

A Parwani

Publications and source records attributed to A Parwani.

9 recordsLinked to original sources
PubMed2005

Gait evaluation: a tool to monitor bone healing?

BACKGROUND: Current clinical methods for monitoring fracture healing are often invasive and inaccurate. This paper evaluates the use of a pressure sensitive platform to improve monitoring. METHODS: Standardised 3 mm diaphyseal bone defects were created in the right tibia of 64 female sheep and stabilised with either a rigid monolateral external fixator or a more flexible variant. Over a nine week healing period gait parameters were measured using a pressure sensitive platform and interfragmentary movements at the fracture site were monitored. Frequency spectra were calculated for the ground reaction forces. The tibiae were tested biomechanically after sacrifice and callus sections were analysed histomorphometrically. FINDINGS: All animals unloaded the operated and overloaded the contralateral hindlimb. Callus mineralisation and stiffness, as well as limb loading increased during healing whilst interfragmentary movements were reduced. Larger interfragmentary movements resulted in a slower fracture healing rate as documented histologically and biomechanically. Frequency analysis showed upto 14 dB loss of power at frequencies associated with bone mechanotransduction at four weeks postoperatively, reducing to a 3 dB loss at nine weeks. INTERPRETATION: Gait analysis is a valuable tool for monitoring the course of fracture healing. Different fixation stiffnesses caused different initial interfragmentary movements leading to different healing rates. Ground reaction forces were strongly related to the course of callus mineralisation and thus directly reflected the recovery of stiffness at the fracture site. Reduced levels of loading frequencies that may affect bone healing persist to nine weeks postoperatively.

Analysis of Variance↗
PubMed2001

Effects of smoking on acoustic startle and prepulse inhibition in humans.

RATIONALE: Prepulse inhibition of the acoustic startle response (PPI) is a paradigm in which a startle response to an auditory stimulus is reduced when that stimulus is preceded by a lower intensity, non-startling stimulus (prepulse). PPI is used as an operational measure of sensorimotor gating in both humans and other mammals. Acute administration of nicotine enhances PPI in rats, an effect that has been recently demonstrated in humans. OBJECTIVES: We compared PPI in 12 male smokers and 14 male non-smokers tested in four repeat startle sessions across 2 test days in order to examine further the effects of smoking and smoking withdrawal on acoustic startle and PPI. METHODS: In a crossover design, the smokers smoked ad lib or abstained from smoking overnight prior to 9 a.m. testing. These 2 test days were in randomized order. On both days, smokers were immediately retested after smoking three cigarettes. Non-smokers were tested twice on each of 2 separate days. RESULTS: Across sessions, the smokers had reduced startle to pulse alone stimuli in the first block of each session when compared to the non-smokers. The non-smokers had no change in gating across their four test sessions. For the smokers, the abstinence condition produced a non-significant reduction in PPI compared to that of the ad lib smoking day. During the smoking abstinence session, smokers had comparable gating to non-smokers. Smoking immediately after washout produced a significant improvement in PPI such that gating in the smokers exceeded that of the non-smokers. CONCLUSION: Smoking after overnight washout from cigarettes enhanced sensorimotor gating compared to pre-smoking values and compared to gating in non-smokers.

Acoustic Stimulation↗
PubMed2001

Clinical and sensorimotor gating effects of ketamine in normals.

The clinical similarities between PCP psychosis and schizophrenia have contributed importantly to the development of the glutamate hypothesis of schizophrenia. Sensory gating, as measured by prepulse inhibition of the acoustic startle reflex (PPI), is impaired in patients with schizophrenia. In animals, the noncompetitive NMDA antagonists PCP and ketamine disrupt PPI in a way that resembles the defect seen in schizophrenia. The purpose of this work is to investigate the modulation of sensory gating in humans by subanaesthetic doses of ketamine. 16 healthy male subjects received a 60-min infusion of ketamine (0.5 mg/kg) or normal saline on two separate days in a randomized double-blind crossover design. Clinical ratings and PPI were done during the infusion on both days. Ketamine produced robust clinical effects. Dissociative symptoms as measured by the CADSS increased from 0 +/- 0.0 to 29.3 +/- 14.3; negative symptoms (Affect Rating Scale) increased from 17.2 +/- 0.8 to 24.8 +/- 3.1; and total BPRS scores increased from 18.3 +/- 0.8 to 26.4 +/- 5.1. ANOVAs for these ratings were all significant at the p <.000 level, although BPRS increases were not in the range seen in decompensated schizophrenic patients. The amplitudes of the startle responses to pulse-alone stimuli were not significantly different on ketamine and placebo days. Ketamine did not cause disruption in PPI as expected. On the contrary, in the first block of the PPI session ketamine significantly enhanced PPI (ANOVA; F=6.15, p =.026). These results indicate that the clinical effects of ketamine are not coupled with schizophrenic-like disruption of PPI in normal controls.

Adult↗
PubMed2001

Effects of ketamine in normal and schizophrenic volunteers.

This study evaluates the effects of ketamine on healthy and schizophrenic volunteers (SVs) in an effort to define the detailed behavioral effects of the drug in a psychosis model. We compared the effects of ketamine on normal and SVs to establish the comparability of their responses and the extent to which normal subjects might be used experimentally as a model. Eighteen normal volunteers (NVs) and 17 SVs participated in ketamine interviews. Some (n = 7 NVs; n = 9 SVs) had four sessions with a 0.1-0.5 mg/kg of ketamine and a placebo; others (n = 11 NVs; n = 8 SVs) had two sessions with one dose of ketamine (0.3 mg/kg) and a placebo. Experienced research clinicians used the BPRS to assess any change in mental status over time and documented the specifics in a timely way. In both volunteer groups, ketamine induced a dose-related, short (<30 min) increase in psychotic symptoms. The scores of NVs increased on both the Brief Psychiatric Rating Scale (BPRS) psychosis subscale (p =.0001) and the BPRS withdrawal subscale (p =.0001), whereas SVs experienced an increase only in positive symptoms (p =.0001). Seventy percent of the patients reported an increase (i.e., exacerbation) of previously experienced positive symptoms. Normal and schizophrenic groups differed only on the BPRS withdrawal score. The magnitude of ketamine-induced changes in positive symptoms was similar, although the psychosis baseline differed, and the dose-response profiles over time were superimposable across the two populations. The similarity between ketamine-induced symptoms in SVs and their own positive symptoms suggests that ketamine provides a unique model of psychosis in human volunteers. The data suggest that the phencyclidine (PCP) model of schizophrenia maybe a more valid human psychosis/schizophrenia drug model than the amphetamine model, with a broader range of psychotic symptoms. This study indicates that NVs could be used for many informative experimental psychosis studies involving ketamine interviews.

Adult↗
PubMed2000

Impaired prepulse inhibition of acoustic startle in schizophrenia.

BACKGROUND: Schizophrenics show deficits in sensorimotor gating, as measured by prepulse inhibition of acoustic startle (PPI). The goal of this investigation is to further characterize PPI and habituation deficits in schizophrenia, and to examine whether differing subgroups of schizophrenics would show comparable PPI deficits. METHODS: PPI was measured in 24 male schizophrenic subjects (9 acutely decompensated inpatients and 15 stable outpatients) and in 20 age-matched normal control subjects. Schizophrenic subjects were rated for positive and negative symptoms at the time of testing. RESULTS: Schizophrenic subjects showed deficits in prepulse inhibition and habituation as compared to normal subjects. Similar latency facilitation was produced by the prepulse in both groups. Acutely decompensated inpatients and stable outpatients did not differ in percent PPI. PPI did not correlate with severity of positive or negative symptoms. CONCLUSIONS: These results suggest that schizophrenic subjects have impaired central inhibitory mechanisms as measured by PPI, and support the hypothesis that periods of relative clinical remission are not accompanied by normalization of sensorimotor gating.

Acoustic Stimulation↗
PubMed2000

Development of a reverse transcription-nested polymerase chain reaction assay for differential diagnosis of transmissible gastroenteritis virus and porcine respiratory coronavirus from feces and nasal swabs of infected pigs.

Transmissible gastroenteritis virus (TGEV), a coronavirus, replicates in intestinal enterocytes and causes diarrhea in young pigs. Porcine respiratory coronavirus (PRCV), a spike (S) gene natural deletion mutant of TGEV, has a respiratory tissue tropism and causes mild or subclinical respiratory infections. Conventional antigen-based diagnostic tests fail to differentiate TGEV and PRCV, and a blocking ELISA test to serologically differentiate TGEV/PRCV-infected pigs is conducted on convalescent serum retrospectively after disease outbreaks. A reverse transcription (RT)-nested polymerase chain reaction (PCR) with primers targeted to the S gene deletion region to differentiate TGEV/PRCV was developed. The specificity of the RT-nested PCR was confirmed with reference and recent field strains of TGEV/PRCV, and its sensitivity was analyzed by testing nasal and fecal samples collected from pigs at various days postinoculation (DPI) with TGEV or PRCV. Specific PCR products for TGEV/PRCV were detected only with the homologous reference or field coronaviruses and for 10-14 DPI of pigs with TGEV (feces) or PRCV (nasal samples). The RT-nested PCR assay was more sensitive than antigen-based assays on the basis of duration of virus detection in experimentally infected pigs and was directly applicable to nasal as well as fecal specimens from the field.

Animals↗
PubMed1996

Rotavirus subunit vaccines.

We evaluated rotavirus subunit vaccines for use in humans and animals. Insect cells were co-infected with combinations of individual baculovirus recombinants expressing human, bovine or simian rotavirus VP2, VP4, VP6 or VP7 to produce virus-like particles (VLPs). To determine whether immunization with VLPs could induce active protective immunity, VLPs were administered parenterally to rabbits, and the immune response and protection from rabbit ALA rotavirus challenge were evaluated. Complete or partial protection was attained, showing that parenteral immunization with VLPs induces active protective immunity. We also examined whether heterotypic immune responses could be induced with a limited number of broadly reactive VP7 proteins or with chimeric particles (multiple VP7 types on individual particles). The feasibility of this approach was determined by immunizing mice with VLPs containing a G3 VP7 or G1 VP7 and chimeric G1/G3 VLPs. Broadly reactive neutralizing antibody was induced by the G1 VLPs. VLPs also have been successfully used to boost lactogenic (colostral and milk) immunity in dairy cows. Taken together, these results show that VLPs can be effective immunogens in rabbits, mice and dairy cattle when administered parenterally, a limited number of VLPs may be sufficient to produce a broadly protective vaccine, and G3 VLPs may serve as an effective subunit vaccine for use in bovines.

Animals↗
PubMed1991

Characterization of the spontaneous mutant H-2Kbm29 indicates that gene conversion in H-2 occurs at a higher frequency than detected by skin grafting.

A spontaneous mutation of H-2Kb, Kbm29, was discovered among the progeny of F1 hybrid parents. Unlike other characterized spontaneous class I variants, this mutant was detected with the use of antibody, rather than tissue grafting. Although Kbm29 is serologically indistinguishable from the previously described mutant molecule Kbm3, it is identical to the parental Kb by skin grafting and CTL assays. A full length cDNA of Kbm29 was amplified by polymerase chain reaction with locus-specific primers, cloned, and sequenced. Two nucleotides were found to be mutated, resulting in a single amino acid change (Lys----Ala) at amino acid 89 of the mature glycoprotein. This is consistent with the observed serologic changes, as the same amino acid substitution is responsible for the serologic profile of Kbm3. The occurrence of a mutation which is not detectable by the methods normally used to screen for H-2 mutants provides evidence that the high spontaneous rate of structural mutation described for the Kb molecule is underestimated.

Amino Acid Sequence↗