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Biomedical subjects

H Richardson

Publications and source records attributed to H Richardson.

At least 19 recordsLinked to original sources
PubMed1992

Cyclin-B homologs in Saccharomyces cerevisiae function in S phase and in G2.

We have cloned four cyclin-B homologs from Saccharomyces cerevisiae, CLB1-CLB4, using the polymerase chain reaction and low stringency hybridization approaches. These genes form two classes based on sequence relatedness: CLB1 and CLB2 show highest homology to the Schizosaccharomyces pombe cyclin-B homolog cdc13 involved in the initiation of mitosis, whereas CLB3 and CLB4 are more highly related to the S. pombe cyclin-B homolog cig1, which appears to play a role in G1 or S phase. CLB1 and CLB2 mRNA levels peak late in the cell cycle, whereas CLB3 and CLB4 are expressed earlier in the cell cycle but peak later than the G1-specific cyclin, CLN1. Analysis of null mutations suggested that the CLB genes exhibit some degree of redundancy, but clb1,2 and clb2,3 cells were inviable. Using clb1,2,3,4 cells rescued by conditional overproduction of CLB1, we showed that the CLB genes perform an essential role at the G2/M-phase transition, and also a role in S phase. CLB genes also appear to share a role in the assembly and maintenance of the mitotic spindle. Taken together, these analyses suggest that CLB1 and CLB2 are crucial for mitotic induction, whereas CLB3 and CLB4 might participate additionally in DNA replication and spindle assembly.

Amino Acid Sequence↗
PubMed1992

Secretion of intravenously administered antibiotics in gastric juice: implications for management of Helicobacter pylori.

AIMS: To study whether differences in eradication rates of antibiotics may be explained by differences in secretion of antibiotics in gastric juice. METHODS: A single intravenous dose of either ampicillin 500 mg, erythromycin 500 mg, or metronidazole 500 mg was administered to four healthy Helicobacter pylori negative volunteers on different days. Antibiotic concentrations were measured in gastric juice before and every 10 minutes after administration of the drug for two hours and after one hour in serum. RESULTS: No ampicillin was detected in gastric juice. Erythromycin concentrations in gastric juice showed considerable individual variation and reached maximum concentrations of 2.2-4.8 mcg/ml between 30 and 80 minutes after dosing. Metronidazole concentrations in gastric juice showed much less individual variation and maximum concentrations of 5-6 mcg/ml were reached within 30 minutes and remained high during the study period. CONCLUSION: Metronidazole and erythromycin are secreted across the gastric mucosa, but ampicillin is not.

Adult↗
PubMed1991

A fission yeast B-type cyclin functioning early in the cell cycle.

We have cloned a fission yeast gene, cig1+, encoding a 48 kd product that is most similar to cyclin B proteins. The cig1+ protein has a "cyclin box" approximately 40% identical to B-type cyclins of other species, but lacks the "destruction box" required for proteolysis of mitotic cyclins. Deletion of cig1+ had no observable effect on cell viability or progression through G2 or M phase, but instead caused a marked lag in the progression from G1 to S phase. G1 constituted approximately 70% of the cell cycle in cig1 deletion strains, as compared with less than 10% in cig1+ strains. Constitutive cig1+ overexpression was lethal, causing cessation of growth and arrest in G1. Expression of cig1+ failed to rescue an S. cerevisiae strain lacking CLN Start cyclins. Thus, cig1+ identifies a new class of B-type cyclin acting in G1 or S phase that appears to be functionally distinct from all previously described cyclin proteins.

Amino Acid Sequence↗
PubMed1991

The accuracy of clinical findings and laparoscopy in pelvic inflammatory disease.

The accuracy of clinical diagnosis for pelvic inflammatory disease was determined in 95 women who presented with pelvic pain to primary care physicians and then were referred to gynecologists. Laparoscopy or laparotomy with endometrial biopsy and fimbrial minibiopsy revealed that prevalence of pelvic inflammatory was 46% (44/95) and positive and negative predictive values of gynecologists were 74% (23/31) and 67% (43/64) (p = 0.0002). If histopathologic diagnosis was the standard, clinical accuracies of the gynecologists were no better than chance (p = 0.43), suggesting an expectation bias for visual diagnosis. Laparoscopy had a sensitivity of 50% (12/24) and a specificity of 80% (40/50) for salpingitis if the standard was fimbrial histopathologic diagnosis (p = 0.01). These results support the routine use of laparoscopy, supplemented when negative by endometrial and fimbrial minibiopsy, to accurately diagnose pelvic inflammatory disease.

Cervix Uteri↗
PubMed1991

Massive thyroid oncocytoma.

A patient with a massive thyroid oncocytoma is presented. The symptoms of hoarseness and dysphagia were due to compression and were relieved by surgical excision of the tumour.

Adenoma↗
PubMed1991

cdc25 M-phase inducer.

In this paper, we have described the critical experiments leading to the discovery and analysis of the cdc25 M-phase inducer. We have shown that timing of mitosis is sensitive to the level of cdc25+ expression and that the cellular concentration of p80cdc25 increases as cells approach mitosis. From these observations we conclude that, in S. pombe, rate of accumulation of p80cdc25 plays an important role in determining the timing of mitosis. We postulate that under a given set of conditions, a critical level of p80cdc25 activity is required to undergo mitosis. The actual level that is required can vary depending on ploidy, growth rate, nutritional status of the cell, and perhaps other parameters. These signals may be monitored through the weel pathway leading to tyrosyl phosphorylation of p34cdc2. We have shown that p80cdc25 encodes a phosphate that acts by directly dephosphorylating the Tyr-15 residue of p34cdc2. Our studies strongly indicate that this aspect of the mitotic control network is generally conserved among eukaryotes. It is conceivable, however, that the mode of regulation of cdc25 activity may vary from species to species. Clearly, in S. cerevisiae the cdc25+ homolog, MIH1, in contrast to cdc25+, is not rate-limiting for M-phase onset. It will be important to determine whether the level of cdc25+ homologs in other organisms also oscillates during the cell cycle, or whether their activity is controlled by localization or posttranslational mechanisms, such as phosphorylation. Furthermore, our finding of more than one cdc25+ homolog in a single species suggests an additional level of complexity to the control of M-phase onset by cdc25 in higher eukaryotes that will require further investigation.

Amino Acid Sequence↗
PubMed1990

Human homolog of fission yeast cdc25 mitotic inducer is predominantly expressed in G2.

Entry into mitosis during the somatic cell cycle is regulated in response to signals that monitor the completion of DNA replication, the integrity of the nuclear genome, and, possibly, the increase in cellular mass during the cell cycle. It has been postulated that the operation of this cell cycle control involves the gradual accumulation of rate-limiting mitotic inducers, which trigger nuclear division when their cellular concentration reaches a critical level. We have cloned a human gene, which we call CDC25, whose product may function as a mitotic inducer. This human gene encodes a protein with a predicted molecular mass of 53,000 daltons whose C-terminal domain shares about 37% sequence identity with the fission yeast cdc25+ mitotic inducer. The human CDC25 gene rescues the defect of a fission yeast temperature-sensitive (ts) cdc25ts mutant that is unable to initiate mitosis. In HeLa cells CDC25 mRNA levels are very low in G1 and increase at least 4-fold as cells progress towards M phase. These data suggest that in human cells, as in fission yeast, the accumulation of CDC25 mitotic inducer during G2 may play a key role in regulating the timing of mitosis.

Amino Acid Sequence↗
PubMed1990

A rapid method for detection of group B streptococcal colonization: testing at the bedside.

Vertical transmission of group B streptococci, the most frequent cause of early neonatal sepsis, can be interrupted by intrapartum antibiotics. However, rapid methods for detecting colonized women must be developed to limit the administration of antibiotics to those who are at risk of delivering an infected infant. The accuracy of a colorimetric test using starch serum medium on vaginal and rectal specimens from women with preterm labor or prolonged rupture of membranes was evaluated. The test was interpreted by labor and delivery room nurses without special microbiologic training. Starch serum medium results were compared with those obtained from routine cultures. Thirteen of 29 positive vaginal cultures (45%) and eight of 18 positive rectal swabs (44%) were identified by nurses using the rapid method. This was significantly different (P less than .001) from sensitivities of 93 and 95%, respectively, for the same vaginal and rectal specimens interpreted by a bacteriology technologist. The specificity for the test from both sites was 95% for the nurses. The sensitivity was 53 and 36% for vaginal and rectal swabs, respectively, for a subgroup of mothers whose infants were assessed as clinically septic. The low sensitivity of starch serum medium as interpreted by nurses in the labor suite is inadequate to allow the test to replace cultures in identifying women colonized with group B streptococci. Efforts to increase the sensitivity should be directed toward improving nursing staff interpretation rather than improving the medium itself.

Colorimetry↗
PubMed1989

DNA replication studies with coliphage 186. II. Depression of host replication by a 186 gene.

Using pre-labelling rather than pulse-labelling studies to determine rates of replication, we have shown that coliphage 186 infection is accompanied by a depression in host DNA replication. We have isolated mutants of the phage gene involved and mapped them in the early region of the phage genome. Sequencing the mutants ultimately led us to the identification of the gene that we have named the dhr gene.

Base Sequence↗
PubMed1989

Optimization of a medium for the rapid urease test for detection of Campylobacter pylori in gastric antral biopsies.

We developed a buffered azide-free urea medium which is sensitive, specific, and nontoxic for rapid detection of Campylobacter pylori in gastric biopsies. Detection of urease produced by the organism provides the basis for the test. The substrate is urea in monobasic sodium phosphate buffer, and phenol red provides indication of the pH change that results from urease activity. A rapid change from yellow to red occurs in the presence of C. pylori, even at low concentrations of the organism. A slower color change occurs with higher concentrations of other urease producers, such as Yersinia enterocolitica and Proteus mirabilis. Experience with 51 patients with our medium showed excellent results in detection of C. pylori in gastric mucosal biopsies. In clinical research and practice, a rapid bedside test will be helpful for rapid diagnosis of C. pylori-positive patients.

Azides↗
PubMed1989

Volatile substance abuse: evaluation and treatment.

1. A scheme for the identification and evaluation of volatile substance abusers is outlined which emphasizes the need for medical history, drug history, emotional/behavioural and dependency questionnaires and physical examination. 2. Poor initial evaluation may lead to non-recognition of dependent abusers who may present later with more serious problems. 3. Suggestions for prevention and treatment of chronic abusers are discussed and some advice for parents is outlined.

Adolescent↗
PubMed1988

Sequential treatment of a simple pneumothorax.

In a prospective investigation of isolated simple pneumothorax, the treatment of 35 patients with a total of 37 pneumothoraces was studied. A standardized sequential treatment approach was followed for evacuation of the pneumothorax and maintenance of lung reexpansion. The protocol involved catheter placement using a Seldinger technique, aspirations, and documentation of reexpansion by chest radiography and observation. Reaccumulation of air was treated with Heimlich valve attachment to the catheter at intrapleural pressure and further observation. Continued air leak following Heimlich valve attachment was treated with chest catheter suction using a Pleurovac at -20 cm H2O pressure. Chest tube thoracostomy was performed for continued failure of reexpansion. In 22 of the 37 pneumothoraces (59%) simple catheter aspiration maintained lung reexpansion without complications. In the remaining 15 pneumothoraces (41%), seven (47%) responded to Heimlich valve attachment, and three (20%) maintained expansion with chest catheter suction. Chest tube thoracotomy was required to maintain expansion in 33% (five) of those who failed catheter suction (14% of all pneumothoraces studied). Patients treated successfully with simple catheter aspiration were sent home. Patients requiring a Heimlich valve, chest catheter suction, or chest tube thoracostomy were hospitalized. Use of these catheter techniques resulted in lower cost and was associated with shorter hospitalizations than in chest tube thoracostomy. Our study suggests that sequential treatment of simple pneumothorax should be considered as a cost-effective and therapeutically successful alternative to immediate chest thoracostomy in selected cases.

Adolescent↗
PubMed1988

Rapid detection of group B streptococcal carriage in parturient women using a modified starch serum medium.

Group B streptococcal disease is the most frequent infectious cause of morbidity and mortality of newborns in North America. There is evidence that vertical transmission, the major route of neonatal acquisition, may be interrupted by administration of antibiotics during the intrapartum period. A modified starch serum medium has been developed that will allow the rapid identification of group B streptococci, by observation of a color change, in vaginal and rectal swabs. This medium was compared to a "gold standard" of routine culture. The sensitivity and specificity of the test were found to be 100% and 99%, respectively, in 237 specimens from women attending different clinics who submitted vaginal swabs. All color changes occurred within 6 hours. Vaginal and rectal carriage of the organism were found in 8% and 12%, respectively, of women in preterm labor. In this population the sensitivity and specificity of the test for vaginal specimens were 97% and 98%, respectively. The corresponding values for rectal swabs were 94% and 100%. The test can potentially select carrier mothers who could benefit the most from intrapartum antibiotics. This medium may also be used for transport to enhance detection of colonization.

Anti-Bacterial Agents↗