Structure and Function of the Kidney in Septic Shock. A Prospective Controlled Experimental Study

RATIONALE

It is unclear how septic shock causes acute kidney injury (AKI) and whether this is associated with histological change.

OBJECTIVES

We aimed to determine the nature and extent of changes in renal structure and function over time in an ovine model of septic shock.

METHODS

Fifteen sheep were instrumented with a renal artery flow probe and renal vein cannula. Ten were given intravenous Escherichia coli to induce septic shock, and five acted as controls. Animals were mechanically ventilated for 48 hours, while receiving protocol-guided parenteral fluids and a norepinephrine infusion to maintain mean arterial pressure. Renal biopsies were taken every 24 hours or whenever animals were oliguric for 2 hours. A renal pathologist, blinded to tissue source, systematically quantified histological appearance by light and electron microscopy for 31 prespecified structural changes.

MEASUREMENTS AND MAIN RESULTS

Sheep given E. coli developed septic shock, oliguria, increased serum creatinine, and reduced creatinine clearance (AKI), but there were no changes over time in renal blood flow between groups (P > 0.30) or over time within groups (P > 0.50). Renal oxygen consumption increased only in nonseptic animals (P = 0.01), but there was no between-group difference in renal lactate flux (P > 0.50). There was little structural disturbance in all biopsies and, although some cellular appearances changed over time, the only difference between septic and nonseptic animals was mesangial expansion on electron microscopy.

CONCLUSIONS

In an intensive care-supported model of gram-negative septic shock, early AKI was not associated with changes in renal blood flow, oxygen delivery, or histological appearance. Other mechanisms must contribute to septic AKI.

Abstract P1-14-05: Three distinct HER2 subtypes identified by BluePrint 80-gene functional subtyping predict treatment-specific response in the prospective neo-adjuvant NBRST registry

Background

Ideally classification by subtype predicts treatment response and overall outcome. BluePrint 80-gene functional molecular subtype is based on mRNA expression (as is intrinsic subtype) associated with intact translation to protein (unlike intrinsic subtype). BluePrint (BP) classifies patients into Luminal, Her2 or Basal-type. Presently subtype is approximated using conventional immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) ("conventional subtype") or assigned by gene expression profiling. The main objective of the prospective neo-adjuvant NBRST study is to compare drug sensitivity as defined by pathological Complete Response (pCR), using 80-gene functional subtype vs. conventional IHC/FISH subtyping. NBRST enrolled over 1,000 US patients between June 2011 and December 2014. In this analysis we present the results for IHC/FISH Her2-positive patients.

Methods

Here we report findings in the 260 NBRST patients who had IHC/FISH Her2+ breast cancer, according to ASCO CAP guidelines at the time of diagnosis. Treatment, including chemotherapy and HER2-targeted agents, was at the discretion of the physician adhering to NCCN approved or other peer-reviewed, established regimens over the course of the study. pCR was defined as T0/isN0. Fisher's exact test was used to compare pCR rates among IHC/FISH and functional subtypes and treatment groups.

Results

The 260 IHC/FISH Her2+ patients had median age 53 (range 23-81) and included T1-4, N0-3 tumors. Of 169 ER+/Her2+ tumors 49% were re-classified as BP Luminal, 43% as BP HER2, and 8% as BP Basal. The median ER% of ER+/Her2+/BP Luminal tumors was 93% (range 3-100), compared to 79% in ER+/Her2+/BP HER2 (range 1-91) and 8% in ER+/Her2+/BP Basal-type (range 2-99).The overall pCR rate in ER+/Her2+/BP Luminal was 17% (4% with chemo/trastuzumab; 39% chemo/trastuzumab/pertuzumab, p<0.0001) and statistically inferior (p<0.0001) to the 59% pCR rate in ER+/Her2+/BP HER2. Of 91 ER-/Her2+ tumors 74% were classified as BP HER2, 25% were re-classified BP Basal and <1% was BP Luminal. NCT pCR rates for ER-/Her2+/BP HER2 was 67% (64% with chemo/trastuzumab; 77% chemo/trastuzumab/pertuzumab, p=0.40) and significantly superior (p=0.026) to the 39% pCR rate in ER-/Her2+/BP Basal (p=0.026).

Conclusions

In the NBRST study, BP 80-gene functional subtype (based on mRNA expression and translation): 1. Re-classifies over half of all IHC/FISH ER+/Her2+ patients; 2. Predicts treatment response or resistance in Her2+ patients not segregated by conventional IHC/FISH classification and 3. Identifies ER+/Her2+ tumors that are sensitive to chemo/trastuzumab/pertuzumab but resistant to chemo/trastuzumab.

Citation Format: Whitworth P, Beitsch P, Baron P, Beatty J, Pellicane JV, Murray MK, Dul CL, Mislowsky AM, Nash CH, Richards PD, Lee LA, Stork-Sloots L, de Snoo F, Untch S, Gittleman M, Akbari S, Rotkis MC. Three distinct HER2 subtypes identified by BluePrint 80-gene functional subtyping predict treatment-specific response in the prospective neo-adjuvant NBRST registry. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-14-05.

Abstract P4-14-10: Pertuzumab overcomes chemotherapy/trastuzumab resistance in ER+/Her2+ tumors classified as luminal functional subtype by the 80-gene BluePrint assay in the prospective neo-adjuvant breast registry symphony trial (NBRST)

Background

The prospective Neo-adjuvant Breast Registry Symphony Trial (NBRST) enrolled over 1000 US patients between June 2011 and December 2014. The aim of NBRST study is to compare chemosensitivity as defined by pathological Complete Response (pCR) using the 80-gene BluePrint functional subtype profile vs. conventional IHC/FISH subtyping. Treatment was at the discretion of the physician utilizing standard NCCN regimens. Pertuzumab, a monoclonal antibody, inhibits the dimerization of HER2 with other HER receptors. Pertuzumab received US FDA approval for the neo-adjuvant treatment of HER2-positive breast cancer in September 2013. Essentially all patients with HER2 positive cancers were treated with chemotherapy + trastuzumab and after this date pertuzumab was added, creating 2 distinct groups of Her2 treated patients.

The aim of the current analysis is to compare the pCR rate of trastuzumab (H) vs trastuzumab and pertuzumab (H + P) by conventional and BluePrint functional subtype.

Methods

The current analysis includes women from the NBRST study, with histologically proven breast cancer, who received neo-adjuvant chemotherapy plus H or H + P and who provided written informed consent. Pathological assessment of Her2 was done according to ASCO CAP guidelines at the time of diagnosis. BluePrint (BP) classifies patients into Luminal, HER2 or Basal-type. pCR is defined as T0/isN0. All pCRs were verified with a de-identified copy of the surgical pathology report. Fisher's exact test was used to compare pCR rates within different subgroups.

Results

252 IHC/FISH Her2+ patients received H (166) or H + P (86). The median age was 53 (range 23-81). 8% was stage I, 68% stage II and 24% stage III. 65% were ER positive.

BP classified 55% of patients as HER2, 32% as Luminal, and 14% as Basal-type.

The pCR rates and p-values within different subgroups of clinical Her2+ patients are provided in the table below.

pCR rates and p-values within different subgroups of clinical Her2+ patients(n)H (pCR rate)H + P (pCR rate)p-valueTotal (n=252)40%59%0.005IHC/FISH Her2+/ER+ (163)30%57%0.001IHC/FISH Her2+/ER- (89)69%63%0.82BP HER2 (138)57%78%0.01BP Luminal (80)4%38%0.0002BP Basal (34)47%38%0.69

Conclusions

Addition of pertuzumab to trastuzumab significantly increased response rate in ER+/Her2+, BP HER2 and BP Luminal patients but not in ER-negative and BP Basal patients.

Pertuzumab overcame resistance to NCT/trastuzumab in a substantial proportion of the IHC/FISH Her2+/BP Luminal subgroup; indicated by a significantly increased pCR rate.

Citation Format: Peter B, Pat W, Paul B, Jennifer B, Pellicane JV, Murray MK, Dul CL, Mislowsky AM, Nash CH, Richards PD, Lee LL, Stork-Sloots L, de Snoo F, Untch S, Gittleman M, Akbari S, Rotkis MC. Pertuzumab overcomes chemotherapy/trastuzumab resistance in ER+/Her2+ tumors classified as luminal functional subtype by the 80-gene BluePrint assay in the prospective neo-adjuvant breast registry symphony trial (NBRST). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-10.

Abstract P4-14-29: One-third of HER2 positive patients have 80-gene luminal subtype that is resistant to chemo-trastuzumab but sensitive to chemo-trastuzumab-pertuzumab: Critical implications for the adjuvant setting from the NBRST phase 4 neoadjuvant study

Background

The phase 4 Neo-adjuvant Breast Registry Symphony Trial (NBRST) enrolled over 1,000 US patients between June 2011 and December 2014. The aim of NBRST study is to compare chemo-sensitivity as defined by pathological Complete Response (pCR) using the 80-gene BluePrint (BP) functional subtype profile vs. conventional IHC/FISH subtyping. Treatment was at the discretion of the physician utilizing standard NCCN regimens. Pertuzumab, a monoclonal antibody, inhibits the dimerization of HER2 with other HER receptors. Pertuzumab received US FDA approval for the neo-adjuvant treatment of HER2-positive breast cancer in September 2013. Essentially all patients with HER2 positive cancers were treated with chemotherapy + trastuzumab and after this date pertuzumab was added, creating 2 distinct groups of Her2-treated patients.

The aim of the current analysis is to compare the pCR rate of chemo-trastuzumab (c-t) vs chemo-trastuzumab plus pertuzumab (c-t-p) by conventional and 80-gene BP functional subtype. 80-gene BP functional subtype was derived by supervised cluster analysis for concordant mRNA and protein expression.

Methods

The current analysis includes women from the NBRST study, with histologically proven breast cancer, who received neo-adjuvant treatment, had 80-gene subtyping and provided written informed consent. Pathological assessment of HER2 was performed according to ASCO CAP guidelines at the time of diagnosis. 80-gene BluePrint (BP) classifies patients into Luminal, HER2 or Basal-type. pCR is defined as T0/isN0. All pCRs were verified with a de-identified copy of the surgical pathology report. Fisher's exact test was used to compare pCR rates within different subgroups.

Results

286 IHC/FISH HER2+ patients received c-t (175) or c-t-p (111). Of these 80-gene BP subtype classified 53% as HER2-type, 33% as Luminal-type and 14% as Basal-type. 64% were ER positive.

The pCR rates and p-values within different subgroups of clinical HER2+ patients are provided in the table below.

 c-tc-t-p (n)pCR ratep-valueTotal (n=286)41%57%0.01BP HER2 (153)58%73%0.06 BP Luminal (93) 6% 39% 0.0002BP Basal (40)45%1.0IHC/FISH HER2+/ER+ (183)31%53%0.003IHC/FISH HER2+/ER- (103)59%64%0.68

Conclusions

One-third of ASCO/CAP Her2+ patients had 80-gene BP Luminal subtype and demonstrated resistance to c-t (pCR 6%). Addition of Pertuzumab overcame resistance in this group (pCR 39%). This finding in the neoadjuvant setting suggests a substantial potential benefit in the adjuvant setting and thus an urgent need to consider treatment in at-risk patients as well as confirmatory tissue analysis from independently reported trials.

Citation Format: Beitsch P, Whitworth P, Baron P, Beatty J, Pellicane JV, Murray MK, Dul C, Mislowsky AM, Nash CH, Richards PD, Lee LA, Stork-Sloots L, de Snoo F, Untch S, Gittleman M, Akbari S, Rotkis MC. One-third of HER2 positive patients have 80-gene luminal subtype that is resistant to chemo-trastuzumab but sensitive to chemo-trastuzumab-pertuzumab: Critical implications for the adjuvant setting from the NBRST phase 4 neoadjuvant study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-29.

Aridicins, novel glycopeptide antibiotics. I. Taxonomy, production and biological activity

A new species of a new genus of the Actinomycetales was discovered, Kibdelosporangium aridum. This strain produces a new family of glycopeptide antibiotics designated aridicins, that contain an unusual glycolipid constituent. They inhibit Gram-positive bacteria, including staphylococci, enterococci and Clostridium sp.

Physical characterization of plasmids isolated from Streptosporangium

Plasmids were isolated from two species of Streptosporangium by CsCl-ethidium bromide equilibrium density gradient centrifugation. A plasmid isolated from S. brasiliense, designated pSgB-1, was characterized by electron microscopy and agarose gel electrophoresis. The pSgB-1 plasmid is a closed circular DNA molecule of 9.4 X 10(6) Da. A restriction endonuclease map was generated and unique cleavage sites were found for EcoRI, ClaI, XbaI, and MstII. Another plasmid, pSgV-1, isolated from S. viridognriseum, has an estimated Mr of 54 X 10(6). The pSgB-1 plasmid is phenotypically cryptic but an unusual phenotypic trait, resembling phage plaques, may be associated with the S. viridogriseum plasmid pSgV-1.

Virus-like particles and lytic plaque formation in lawns of Candida albicans

The antifungal agent Aculeacin A at subinhibitory levels induced lytic plaques in lawns of Candida albicans. Electron microscopic examination of plaque lysates suspended in phosphotungstic acid revealed the presence of spherical particles 12, 18, and 28 to 30 nm in size. Particles were also found in ultrathin sections of treated C. albicans cells. The plaque lysate lost infectivity after treatment with UV light, heat treatment at 80 degrees C for 10 min, or being held at pH 2 for 30 min.

Aculeacin A resistant mutants of Candida albicans

Mutants of Candida albicans resistant to aculeacin A, a yeast cell-wall inhibitor, were isolated after mutagenesis with ultraviolet light. The parental strain was sensitive to 0.1 approximately 0.5 microgram/ml of the antibiotic. In contrast, the minimum inhibitory concentration for the mutants ranged from 50 to 200 microgram/ml. Except for papulocandin, another cell-wall inhibitor, the antibiotic susceptibility of the mutants was similar to the parental strain. The parent strain and the aculeacin resistant mutants exhibited similar morphological changes at subinhibitory levels of aculeacin and had comparable growth rates on complex media. The lipid and sterol content of the parent and the mutants were significantly different. For example, the total lipid content was two-fold higher in the mutant strains. Drug resistance in the mutants was specific for aculeacin and papulocandin and appeared to be associated with alteration in the lipid composition of membranes.

Influence of pH on spore aggregation of Streptosporangium brasiliense

Spores of Streptosporangium brasiliense aggregated at acidic pH's and were dissociated into free spores by changing to neutral or alkaline pH's. This finding was utilized in preparing uniform spore suspension, in which simple filtrations gave rise to consistent preparation of free spores at alkaline pH.

Cefonicid: a stable beta-lactamase inhibitor

The stability of cefonicid (SK&F 75073) towards representatives of six major classes of beta-lactamases was determined using a spectrophotometric assay. Cefonicid was stable to hydrolysis by the Type I enzyme from Enterobacter cloacae and by the enzyme from the anaerobe, Bacteroides fragilis. It was 6 to 7 times more stable than cefamandole to the Type IIIA and B enzymes from Escherichia coli, a little less stable than this antibiotic to the Type V enzyme from E. coli, and of equal stability to the Type IV enzyme from Klebsiella aerogenes. Cefonicid was a non-competitive inhibitor (Ki of 0.8 x 10(-6)M) of cephalothin hydrolysis by the Type I enzyme.

Prediction of outcome in metastatic breast cancer treated with adriamycin combination chemotherapy

Univariate and multivariate regression methods were used to analyze 17 potential clinical prognostic factors among 138 patients with advanced breast cancer who received Adriamycin-cyclophosphamide combination chemotherapy between 1973 and 1977 at the University of Arizona. Follow-up of patients was through September 1979, and survival data were nearly complete. Different factors varied in the relationship to outcome, but age, treatment, and response were important. Selecting the three most strongly related factors, predictive regression equations were developed, which described three types of possible outcome: 1) objective response (age, treatment, and liver involvement), 2) freedom from relapse (age, lung involvement, and response), and 3) survival (age, the number of involved sites [less than or equal to 2 or > 2], and treatment). Since use of the regression equations is cumbersome for clinical practice, three simplified tables were constructed to readily predict response, duration of response, and survival before the initiation of treatment.

Fluorescent Staining Technique for Nucleoid Regions of Streptosporangium albidum and Streptosporangium brasiliense

Fluorescent staining procedures were developed for elucidating the nucleoid region in Streptosporangium albidum and Streptosporangium brasiliense. In these procedures, plugs of nutrient agar were inoculated with the microorganims and then covered with a sterile glass slide. The growing cells adhered to the surface of the slide and remained attached throughout the staining procedures. Two separate staining methods were utilized, one with bisbenzimid H33258 and the other with auramine O. Fluorescent microscopy revealed intensely stained nucleoid regions within mycelia, spores, and sporangia.

Relationship between carbon source and susceptibility of Cephalosporium acremonium to selected amino acid analogues

The susceptibility of Cephalosporium acremonium to selected amino acid analogues was markedly influenced by the carbon source used in the test media. Lysine hydroxamate, beta-hydroxy norvaline, and hexafluorovaline were toxic when tested with ribose, ribose or fructose, and ribose or galactose, respectively. In contrast, thialysine and thiaisoleucine inhibited C. acremonium with glucose, fructose, galactose, sucrose, mannitol, sorbitol, and soluble starch. Neither of these analogues was toxic at levels tested when glycerol was used as a carbon source. The minimal inhibitory concentrations (MIC) of thialysine, homoserine, and alpha-methylserine were greater than 1000, greater than 1000, and 250 microgram/mL, respectively, with glycerol. In contrast, the MIC values for the same three analogues were 31, 62, and 125 microgram/mL, respectively, with mannitol. The matching of the carbon sources with the specific amino acid analogues expands the number of analogues useful for selecting derepressed mutants. Thialysine-resistant mutants (tlysR) of C. acremonium which excrete lysine were isolated on a medium containing mannitol.

Mannitol oxidation in two Micromonospora isolates and in representative species of other actinomycetes

Mannitol kinase and mannitol-1-phosphate dehydrogenase activities were detected in two Micromonospora isolates. The presence of these enzyme activities indicates that mannitol is catabolized first to mannitol-1-phosphate and then to fructose-6-phosphate. Mannitol-oxidizing enzymes were also surveyed in representative species of four other genera of actinomycetes. Mannitol-1-phosphate dehydrogenase was detected in cell-free extracts of Streptomyces lactamdurans. In contrast, cell-free extracts of Mycobacterium smegmatis, Nocardia erythrophila, Streptomyces lavendulae, and Actinoplanes missouriensis contained mannitol dehydrogenase activity but no detectable mannitol-1-phosphate dehydrogenase activity. The mannitol dehydrogenase activities in the latter species support the operation of a pathway for catabolism of mannitol that involves the oxidation of mannitol to fructose, followed by phosphorylation to fructose-6-phosphate.

Biosynthesis of mycophenolic acid: purification and characterization of S-adenosyl-L-methionine: demethylmycophenolic acid O-methyltransferase

The final step in the biosynthesis of mycophenolic acid involves the transfer of a methyl group from S-adenosylmethionine to demethylmycophenolic acid. The enzyme, S-adenosylmethionine:demethylmycophenolic acid O-methyltransferase, was isolated from Penicillium stoloniferum and purified 2,700-fold by ammonium sulfate fractionation and diethylaminoethyl-cellulose and Sephadex G-200 chromatography. Maximum enzyme activity was achieved at pH 7.5 and a temperature of 27 to 28 C. The apparent K(m) for demethylmycophenolic acid was 3.1 x 10(-6) M. The enzyme preparation was 50% inactivated when exposed to 33 C for 15 min. Mycophenolic acid, homocystine, S-adenosyl-homocysteine, ethanol, and Mg(2+) inhibited the methyltransferase. This enzyme appears to be subject to end product inhibition which may regulate the synthesis of mycophenolic acid. The methyltransferase activity was highest during the early phases of the fermentation.

Fungal viruses

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Synthesis of cephalosporin C from sulfate by mutants of Cephalosporium acremonium

The innate ability of Cephalosporium acremonium to use methionine preferentially over sulfate for synthesis of cephalosporin C can be influenced through mutation. Mutants of C. acremonium with altered capacity to utilize sulfate for synthesis of antibiotic were isolated and partially characterized with respect to the uptake of sulfate and the regulation of arylsulfatase.

On the mycophage of Penicillium chrysogenum

A mycovirus has been purified from mycelia of Penicillium chrysogenum by isopycnic centrifugation in sucrose and in CsCl. Viral particles band with a buoyant density of 1.20 in sucrose and 1.38 in CsCl. Particles have icosohedral symmetry, are 35 nm in diameter, and have an absorption profile characteristic of nucleoprotein. One enzymatic activity, RNA polymerase, is associated with the purified mycophage. Nucleic acid extracted from purified virus has a buoyant density in CS2SO4 of 1.61, a molar extinction coefficient of εp (258 nm) of 7200, a s20, w of 13.0, and a pattern of circular dichroism characteristic of double-helical ribonucleic acid. Molecules of this double-stranded ribonucleic acid (dsRNA), examined by electron microscopy, have a mean contour length of 0.86 μm which corresponds to a molecular weight of about 2.0 × 106 daltons. This dsRNA is resolved further by acrylamide gel electrophoresis into three closely spaced bands. Thermal denaturation of the viral dsRNA is dependent on ionic strength and gives a linear relationship with the negative logarithm of the sodium ion concentration.

Mutations that affect antibiotic synthesis by Cephalosporium acremonium

The fungus Cephalosporium acremonium produces two β-lactam antibiotics, penicillin N and cephalosporin C. These antibiotics are modified tripeptides derived from α-aminoadipic acid, cysteine, and valine. Mutant strains of C. acremonium fall into four phenotypic classes based on potential to synthesize antibiotics: (A) strains with increased potential to synthesize cephalosporin C, (B) strains unable to synthesize either antibiotic, (C) strains able to synthesize only penicillin N, and (D) strains able to synthesize penicillin N and 6-aminopenicillanic acid. Mutants of the second class, β-lactam negative mutants, have been characterized further. One mutant is auxotrophic for lysine and will synthesize antibiotic only if grown in media supplemented with α-aminoadipic acid or pipecolic acid. Other mutants are prototrophic and consistently negative for antibiotic synthesis. These inactive mutants are further subdivided according to their ability to form peptides implicated as intermediates for the synthesis of β-lactam antibiotics.

Antibiotic synthesis and morphological differentiation of Cephalosporium acremonium

In submerged cultures, Cephalosporium acremonium exists in four morphological forms: hyphae, arthrospores, conidia, and germlings. The phase of hyphal differentiation into arthrospores coincides with the maximum rate of beta-lactam antibiotic synthesis. Furthermore, arthrospores, separated by density-gradient centrifugation, possess 40% greater antibiotic-producing activity than any other morphological cell type. In a series of mutants, each with an increased potential to produce beta-lactam antibiotics, differentiation into arthrospores was proportional to the increased titer of these antibiotics. Thus, arthrospores exhibit enhanced synthesis of beta-lactam antibiotics and appear to be a determining factor in high-yielding mutants. Since a non-antibiotic-producing mutant readily differentiated into arthrospores, antibiotic synthesis and cellular differentiation are not obligately related.

Thermal stability of ribosomes from a psychrophilic and a mesophilic yeast

Ribosomes from the obligately psychrophilic yeast, Candida gelida, are rendered completely non-functional after exposure to 40 C for 5 minutes. This heat-induced impairment of ribosomal function is characterized by a reduced capacity to bind charged sRNA and is accompanied by physical degradation. Ribosomes from the mesophilic yeast, Candida utilis, however, are functionally and physically unaffected when subjected to similar treatment. The dissimilar thermal stabilities may be attributed to marked differences in the ribonucleoproteins present in the two species.

Thermolability of protein synthesis in a cell-free system from the obligately psychrophilic yeast Candida gelida

A subcellular amino-acid-incorporating system from the obligately psychrophilic yeast, Candida gelida, was completely inhibited after incubation at 35 C for 30 minutes. The thermal inactivation of protein synthesis was due, in part, to the presence of unusually temperature-sensitive aminoacyl-sRNA synthetases in C. gelida extracts. Of the 13 specific synthetases examined, 7 retained less than 50% of their activity after being held at 35 C for 30 minutes. Kinetic studies of thermal inactivation of leucyl-sRNA synthetase demonstrated that this enzyme is 50% inactivated after only 7 minutes at 35 C. None of the 10 sRNA species tested was temperature sensitive. In addition to temperature-sensitive synthetases, C. gelida possesses thermolabile soluble enzymes involved in the formation of ribosomal-bound polypeptide chains.

Temperature-sensitive glucose fermentation in the obligately psychrophilic yeast Candida gelida

Fermentation of glucose by resting cells and cell-free extracts of the obligate psychrophile Candida gelida was essentially abolished after being heated for 30 minutes at 35 C. A survey of the enzymes of the yeast alcoholic fermentation pathway revealed that pyruvate decarboxylase was the only temperature-sensitive enzyme. Kinetic studies of thermal inactivation showed that C. gelida pyruvate decarboxylase was 50% inactivated after it was heated for 10 minutes at 35 C. Restoration of glucose fermentation rate in heated extracts from C. gelida, after addition of purified yeast pyruvate decarboxylase, confirmed that heat-induced loss of fermentative activity was due to inactivation of a temperature-sensitive pyruvate decarboxylase.

Thermal injury and death in an obligately psychrophilic yeast, Candida nivalis

Exposure of the obligately psychrophilic yeast, Candida nivalis, to temperatures greater than 20 C, its maximal growth temperature, results in a rapid loss in viability. Furthermore, many of the cells surviving heat treatment are metabolically injured. Injured cells are unable to develop on a glucose – mineral salts – vitamins medium but are able to develop on a complex tryptone – glucose – yeast extract medium. Recovery of injured cells on the complex medium is due to the yeast extract component. Addition of cysteine, reduced glutathione, or thioglycollate to the minimal medium also enhances recovery of heat-injured cells.Additional evidence of heat-induced damage is the release of various cellular components into the suspending menstruum. These include inorganic phosphate, amino acids or short polypeptides, and nucleotide monophosphate. Leakage of these materials into the heating menstruum is not due to cell lysis. The correlation between leakage and loss in viability suggests that membrane damage is at least one factor which determines the low maximal growth temperature of C. nivalis.