Search PubMed⌕ Search

Biomedical subjects

K A Clark

Publications and source records attributed to K A Clark.

At least 19 recordsLinked to original sources
PubMed1995

Synaptic potentiation of dual-component excitatory postsynaptic currents in the rat hippocampus.

1. Whole-cell patch-clamp recording has been used to study tetanus-induced synaptic potentiation of dual-component excitatory postsynaptic currents (EPSCs) in the CA1 region of rat hippocampal slices, following blockade of GABAA and GABAB receptor-mediated synaptic inhibition. 2. At a holding potential of -60 mV, the initial slope of the EPSC (between 10 and 60% of maximum amplitude) provided an accurate measurement of the AMPA receptor-mediated component, and the amplitude of the EPSC at a latency of 100 ms provided the best estimate of the size of the NMDA receptor-mediated component. 3. Neurons were voltage clamped for at least 45 min prior to delivery of a tetanus (test intensity, 100 Hz, 1 s). Measurements at 10 and 30 min following the tetanus were used as indications of short-term potentiation (STP) and long-term potentiation (LTP), respectively. One set of neurons were voltage clamped at -60 mV throughout. These neurons could be subdivided into two populations on the basis of whether or not there was LTP (n = 9), or only STP (n = 6), of the AMPA receptor-mediated component. A second set of neurons were voltage clamped at -60 mV for 30 min and then at -50 mV for 15 min before, during and for 30 min following tetanization. In these experiments there was STP but not LTP (n = 8). 4. In all neurons (n = 23), the time course of the potentiation of the NMDA receptor-mediated component paralleled that of the AMPA receptor-mediated component. In addition, potentiation of the NMDA and AMPA receptor-mediated components were of a similar magnitude. 5. These data demonstrate that it is possible to induce LTP by high frequency stimulation after 45 min of whole-cell recording. Under these conditions, there is a parallel potentiation of the AMPA and NMDA receptor-mediated components of dual-component EPSCs. This constitutes the first evidence, from studies of dual-component synaptic responses, which is consistent with a presynaptic locus of expression of tetanus-induced STP and LTP in the hippocampus.

Animals↗
PubMed1994

Epizootic canine rabies transmitted by coyotes in south Texas.

Prior to 1988, rabies was reported only sporadically in coyotes. However, in the final 4 months of 1988, Starr County, Tex, which is situated on the US-Mexico border, experienced an epizootic of canine rabies, consisting of 6 laboratory-confirmed cases of rabies in coyotes and of 2 cases in domestic dogs. The first 3 cases were detected in coyotes, and the first case in a domestic dog was observed 84 days after the index case. Adjacent Hidalgo County reported 9 cases of rabies in dogs during the same time that rabid dogs were being reported in Starr County. In 1989, the epizootic primarily involved dogs: 15 dogs in Starr County and 19 dogs in Hidalgo County. Five rabid coyotes were reported in Starr County in 1989, and 1 rabid coyote was reported from Hidalgo County. In 1990, rabies was reported in 3 coyotes and in 31 dogs in Starr County; cases were not detected in Hidalgo County. During 1991, the epizootic expanded approximately 160 km northward, resulting in laboratory-confirmed cases in 42 coyotes and 25 dogs in 10 counties. In 1992, Webb and Willacy Counties became involved; 70 rabid coyotes and 41 rabid dogs were reported in 1992 from the 12-county area. During the first 6 months of 1993, there were 31 rabid coyotes and 38 rabid dogs reported from the same 12 south Texas counties. In May 1993, a raccoon infected with the canine rabies ecotype was reported from Cameron County. Antigenic and genetic analysis revealed the virus ecotype affecting dogs and coyotes to be that associated with urban canine rabies along the US-Mexico border.

Animals↗
PubMed1994

A comparison of paired-pulsed facilitation of AMPA and NMDA receptor-mediated excitatory postsynaptic currents in the hippocampus.

Paired-pulse facilitation of excitatory synaptic transmission was investigated in the CA1 region of rat hippocampal slices using whole-cell patch-clamp recording. To optimise the measurement of excitatory synaptic transmission, gamma-amino-butyric acid (GABA)-mediated synaptic inhibition was eliminated using both GABAA and GABAB antagonists. Pure alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs) were then isolated pharmacologically. Paired-pulse facilitation of either AMPA or NMDA receptor-mediated EPSCs (EPSCA and EPSCN, respectively) was investigated using two stimuli of identical strength delivered at intervals of between 25 and 1000 ms. The paired-pulse facilitation profiles of both EPSCA and EPSCN were similar. Paired-pulse facilitation of EPSCA was independent of holding potential. In contrast paired-pulse facilitation of EPSCN was markedly voltage-dependent; maximum facilitation was recorded at hyperpolarised membrane potentials. At positive membrane potentials there was little or no paired-pulse facilitation and, in most neurones, paired-pulse depression was observed. Voltage-dependence of paired-pulse facilitation of EPSCN was similar in the presence of nominal absence of Mg2+ in the bathing medium, and was unaffected by extensive dialysis of neurones with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). These data are consistent with a presynaptic locus for paired-pulse facilitation of EPSCA. However, paired-pulse facilitation of EPSCN involves postsynaptic factors.

Animals↗
PubMed1994

Rate and predictors of prepubertal bipolarity during follow-up of 6- to 12-year-old depressed children.

OBJECTIVE: To investigate the rate and predictors of onset of DSM-III bipolar I and bipolar II disorders among 6- to 12-year-old prepubertal subjects with DSM-III major depressive disorder (MDD) who were followed for a 2- to 5-year period. METHODS: This was a prospective, blindly rated study of 79 children with MDD and 31 normal control children matched for age, gender, and socioeconomic status. Subjects and a second informant were assessed at 4-month intervals using the Kiddie Schedule for Affective Disorders and Schizophrenia-Present Episode Version-1986 modified to include 4-month interval ratings and to include DSM-III diagnoses. Family history (FH) was assessed using the FH-Research Diagnostic Criteria obtained from the mother about the subject's first- and second-degree relatives. RESULTS: Bipolarity developed in 31.7% (N = 25) of the children with MDD at a mean age of 11.2 +/- 2.0 years and 80% were prepubertal. Loaded FH and multigenerational FH were significantly associated with bipolar I. Neither prior nor current use of tricyclic antidepressants nor atypical depressive features were predictive. CONCLUSIONS: These findings strongly support the need to educate families of children with prepubertal-onset MDD about the possibility of the emergence of manic and hypomanic symptoms to encourage early recognition and appropriate treatment.

Adolescent↗
PubMed1992

Psychosocial adjustment of patients arriving early at the emergency department after acute myocardial infarction.

The psychosocial functioning of patients arriving at the emergency department with an acute myocardial infarction early enough to be candidates for treatment with thrombolytic agents was compared with that of those arriving later. Patients who arrived within 3 hours were significantly more anxious when assessed 1 week after admission and had a consistently worse pattern of psychosocial adjustment 3 months after hospital discharge than did those who arrived later. The implications of these findings for efforts to improve early arrival at the emergency department, as well as for medical and psychosocial outcomes after acute myocardial infarction, were considered.

Adult↗
PubMed1992

Evaluation of a commercial DNA probe assay for the identification of clinical isolates of Blastomyces dermatitidis from dogs.

A DNA probe assay (AccuProbe, Gen-Probe, Inc., San Diego, CA) for culture confirmation of Blastomyces dermatitidis in clinical isolates was evaluated using 72 isolates of B. dermatitidis (62 dog isolates, five from other animals, four human isolates and one soil isolate). In addition, specificity determinations were performed using 28 American Type Culture Collection (ATCC) fungal isolates, other than B. dermatitidis, representing 21 different genera. The non-isotopic hybrid protection assay, that can be performed in less than 1 h, uses a chemiluminescent acridinium ester DNA probe that is homologous to ribosomal RNA sequences of B. dermatitidis. Positive results were obtained with all 72 B. dermatitidis isolates (100% sensitivity). In addition, no positive results were evidenced with the other 28 non-B. dermatitidis fungal isolates, including six strains of Histoplasma capsulatum (100% specificity).

Animals↗
PubMed1988

Rabies.

Explore the source record for details and available documents.

Animals↗
PubMed1987

Leprosy in armadillos (Dasypus novemcinctus) from Texas.

Tissue sections from 237 nine-banded armadillos (Dasypus novemcinctus) from 51 central Texas counties were examined microscopically for acid-fast bacilli and/or lesions of leprosy. Neither were found. A review of the literature relative to the incidence of leprosy from armadillos in Texas indicates that residents of counties along the Texas Gulf Coast may be at risk of contracting leprosy by handling infected armadillos or their tissues.

Animals↗
PubMed1986

Team sports for the severely retarded: training a side-of-the-foot soccer pass using a maximum-to-minimum prompt reduction strategy.

A program to teach three severely retarded adults to use a side-of-the-foot soccer pass was evaluated. A 9-step stimulus-response chain was taught using forward chaining. In contrast to usual practice, intensive physical prompts were provided initially to teach each response component, then systematically faded. Approximately 20 lessons (trials) were presented in 20-min sessions. A multiple baseline across subjects design showed that the three trainees achieved the no-prompt criterion after 24, 29, and 22 sessions, respectively. Subanalyses indicated that successive response components were learned only after training was implemented. Follow-up data were obtained 57 and 276 days later in the training room and in a gymnasium; in both settings, criterion was achieved with fewer than three reinstructions.

Cues↗
PubMed1982

Demonstration of monoclonal lymphoplasmacytic proliferations by immunofluorescence on routine formalin-fixed, paraffin-embedded tissue.

This study explores the use of immunofluorescence on routine formalin-fixed paraffin-embedded tissue to distinguish monoclonal from polyclonal lymphoplasmacytic proliferations. Sixteen tissues containing plasma cell or lymphocyte and plasma cell proliferations were studied. Five-micron sections were deparaffinized in xylene, rehydrated, and treated with 0.1% trypsin for two hours. After washing with phosphate-buffered saline, separate sections were stained with fluorescein-conjugated antibody to IgG, IgA, IgM, IgD, and IgE, and a single section was stained with both fluorescein-conjugated anti-kappa and rhodamine-conjugated antilambda. The latter section was useful to distinguish nonspecific adsorption of the fluorochromes. Where possible, results were correlated with immunoelectrophoretic studies of serum and urine. Eleven specimens with monoclonal and four specimens with polyclonal lymphoplasmacytic proliferations were readily identified, including a case of giant lymph node hyperplasia with a monoclonal IgDK plasma cell component (confirmed by specific absorption studies). Identification of monoclonality by immunofluorescence preceded immunoelectrophoretic identification in one case. One other case gave equivocal results by fluorescence. Further, the method worked on formalin-fixed decalcified tissues, although a somewhat heavier background staining was noted. This method offers a simple, reliable technique to establish or confirm the diagnosis of monoclonal lymphoplasmacytic lesions.

Adult↗
PubMed1981

Nesidioblastosis in adults. A surgical dilemma.

Nesidioblastosis is the leading cause of hyperinsulinemia in newborns and infants. To our knowledge, it has not been previously reported in adults unless associated with other diseases. Three males and three females, aged 11 to 57 years, are described. Pancreatic resections ranged from 50% to 100%. Postoperatively, three patients were normoglycemic, two were insulin-dependent diabetics, and one had recurrent hypoglycemia controlled by drugs. The histologic findings in adults were very similar to those in infants with nesidioblastosis. It appears that a minimum resection of 75% to 80% of the pancreas will benefit the majority of patients, alleviating hypoglycemia and preventing the development of diabetes.

Adult↗
PubMed1976

Viral particles associated with malignant catarrhal fever in deer.

Viral particles associated with malignant catarrhal fever in white-tailed deer (Odocoileus virginianus) and axis deer (Asix axis) are described. Morphologically, the virus resembled the togaviruses and was unlike the herpesvirus which causes wildebeest-associated malignant catarrhal fever (snotsiekte).

Animals↗